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When and when not to change heroes-
The mechanism in the game which prevents you from just changing a hero every time you spawn is the charging of ultimate abilities. Charging ultimate abilities carries over from death. Also, certain ultimates as far as i can tell are lost when you change heroes such as the teleporter. Due to this fundamental mechanic when changing heroes, usually its only one person who should change and not a whole team. Also, you want to change when your ultimate timer is low, not when it is close to finishing. Heroes that have low dependence on their ultimate should be first candidates for a change when one is needed.
More specifically, there is a place where certain heroes and "open up" a game. (In paintball terminology) Restated in other words can get kills on key positions that are difficult to get otherwise that make the rest of the team perform well. Often these are based on heroes with aoe ultimates. In general if they are running 4-6 heroes of a certain class, its worth running 2 heroes that counter them, for example, 5 winstons and a mercy, you could run 2 reapers changing out a tracer who has a weaker ultimate. Even though you may think that it is good to change more heroes, for the most part it is better to not change your composition since the strength of your heroes comes from getting to and using your ultimate abilites.
Particularly, some heroes with game changing ultimates are Reaper, Hanzo, Junkrat, D.Va, Mercy and Symmetra. The reaper ultimate pairs with his ability to push in without taking damage than unleash massive aoe around him. Hanzo's scream of ryuu ga waga teki wo kurau unleashes a dragon funnel that passes through walls and basically kills all heroes near the center. Junkrat has a tire that passes around paths and explodes in a ball of aoe on impact. D.va can dash forward, slam her suit onto a point, and unleash it as a ball of aoe. Mercy is great because she can revive her team so you can dive in kill 2 heroes lose 4, then instantly revive the 4 and continue with a 6 on 4. Symmetra has a teleporter which can instantly reinforce forward the team making your team have the spawn position advantage. Thus, often when playing these heroes, you might wait a bit to change just to use your ultimate.
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Key map characteristics and Player movement-
One of the most important things to learn when in a shooting environment is to move and focus on shooting with a purpose. A composition may not work for you that worked for others because of this principle. Certain classes will in general occupy certain areas. Knowing which places will be occupied by both teams will allow more solid coordination. Without understanding the maps and why you are changing positions you cannot do this. A person moves or is killed and it leaves a gap which is exposed when nobody else is able to fill in that gap. Gaps are opportunities that will rapidly turn the game in a teams favor. Being that this is one of the core concepts in explaining compositions, I’ll go over this with a few examples. Looking at shooting before moving,. In choosing where to position and where to move between will usually be to cover a flank, occupy lanes, and hold positions. A common strategy for this is to choose 2 lanes to occupy and shoot into along a wedge. For example, there are two core lanes of fire occupied by the players defending on route 66. The red area is the region where players roam and stay protected, the corners of the wedges are positions that a player moves to add dps into a region the opposing team wants to push.
The units that occupy the space which is being pushed into from the lanes are generally going to be your core army of 3-5 players. (I will start by describing 3 as the core composition, but understand that could be as high as 5.) The remaining mid and back players will support those players with damage or healing will be known here as the dps, since their role is to prevent the other team from pushing onto your core players. The position of the back dps players usually depends on the team strength at that moment. If you are up in players and they are not pushing as hard, DPS players should assume much more aggressive positions which leaves them more exposed, but allows them to offer much more fire power. If your team is down in numbers or the opposing team is pushing hard down a single lane, it is much better to assume a much more defensive posture down a covered position. Thus, identifying when and where pushes will come will help you to identify where you should be to get the most out of your class.
The third concept here is how the map transitions between areas. There are two ideas, one is lane density, the other is player density. In a maps with fewer lanes like route 66, the general composition will either favor spreading out as much as possible in a clearing or pushing through a choke. The choke is a region where many players occupy a similar line in shooting. Ideally this is where high dps, like bastion, widowmaker, will lock in on the enemy army and where most of the challenges will occur in games with a single core. In teams running two shot callers, a clearing will be more challenging because the other team will be in 2 coordinating groups and get the most of out mobility instead of damage.
Lastly some maps will not be so simple and will have many small paths in a small area. These maps are particularly hard for certain compositions which are highly succeptible to flanking or burst damage in a small area of effect. Many lanes exist and holes will be much easier to occur. This happens for example on a map like ilios with high laning density. The core will in general occupy a much larger region and players will need to be able to play more effectively alone rather than with a group.
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Hero classes and basic counters-
This is a section where i’ll go over very briefly each hero, core usage, and counters. Players familiar with the heroes and counters may skip this. Due to that fact, I’ll be using a lot of spoiler tags. In general offense and defense are made to create strenghts in the team, tanks serve some purpose on the map and supports help the team in some core mechanic of play.
Offense-
+ Show Spoiler +
Genji-
Very mobile hero, very good for flanking and using terrain to his benefit.
Attrib:+high mobility lots of dps - low health, not the best ultimate, not very long range
+Bastion (can flank), widow maker (dive past snipes hard to hit), reinhart (flank)
-mei (doesn't have to target), symmetra (has a bunch of small turrets, brings team quickly back to position after a death from flanks), d.va (lots of shots steady damage)
Macree-
Since he reloads so fast and shoots fast for a lot of damage at range, he’s effective at shutting down a lot of close range heroes or hard to hit heroes.
Attrib:+Moderate mobility, fast shooting dps almost no reload time - low health, strong ultimate, good range
+D.va (snap shoot), Mei (can stay at range), Pharah (shoot her out of the sky), Mercy (quickly assault her)
-Roadhog (not a lot of ability to avoid the hook),Winston (can close the distance fast), widowmaker ( basically one shots him)
Pharah-
The rocket aoe and ability to shoot over terrain makes her able to clear out clumped enemies or heroes that rely on shields.
Attrib:+AOE on rocket, Ultimate can clear a section quickly –exposed to a lot of heroes in the air, not very effective at close range.
+Reinhart (Burst down shields), Lucio (can hit him even though he is mobile),Bastion(3 shots him quickly), Torbjorn (kills turret quickly)
-Widowmaker (snipe her quickly), Roadhog(hooks her relatively easily, heals from the rockets), Tracer (rockets almost never hit her), reaper (can push in quickly and avoid damage)
Reaper-
Can move a short distance without getting hit. Has very high dps at close range, maybe best dps at close range in the game.
Attrib:+quick reload time, easily disengages when making mistakes, one of the strongest ultimates in the game –runs slow, not good at range,
+Bastion (can flank, phase through), Lucio (shoots in a region), Winston (can avoid him and rarely misses him)
-Reinhart(Shield him and charge when damge kicks in),Hanzo(use walls to keep distance, faster), Zarya (Gains a lot of damage from shields on her and an ally)
Solider76-
Multiple types of core DPS and ultimate buffs team. Combos well with nearly every hero. Denies Flanking.
Attrib:+Lots of dps, buffs team pushes into lanes -Not overly specialized not usually getting a large amount of burst damage.
+ Tracer (lots of shots, and has aoe secondary rockets), symmetra (denies turrets, can tank a little bit of damage), junkrat (very hard to hit from junkrat, kills ult well), Genji (denies flanking)
- Roadhog (can heal quickly and hook him), Reinhart (cannot shoot through shields), Widowmaker (cannot flank her and does not tank a lot of shots from her)
Tracer-
Super mobile, moderate dps, very good at flanking where ramps are. Not as good on all maps partcularly ones pushing through a point like temple of anubis, or very open terrain like like lijiang tower.
Attrib:+Extreme mobility, can take over a game – High skill cap, medium damage, depends a lot of map
+Bastion (can flank), junkrat(flanks easily, can avoid grenades), reinhart (flanks)
-Torbjorn(turret targets her well), Mei(aoe damage doesn’t have to hit her) , d.va (lots of shots steady damage), soldier 76/reaper (good at denying her a push down a preferred path)
Very mobile hero, very good for flanking and using terrain to his benefit.
Attrib:+high mobility lots of dps - low health, not the best ultimate, not very long range
+Bastion (can flank), widow maker (dive past snipes hard to hit), reinhart (flank)
-mei (doesn't have to target), symmetra (has a bunch of small turrets, brings team quickly back to position after a death from flanks), d.va (lots of shots steady damage)
Macree-
Since he reloads so fast and shoots fast for a lot of damage at range, he’s effective at shutting down a lot of close range heroes or hard to hit heroes.
Attrib:+Moderate mobility, fast shooting dps almost no reload time - low health, strong ultimate, good range
+D.va (snap shoot), Mei (can stay at range), Pharah (shoot her out of the sky), Mercy (quickly assault her)
-Roadhog (not a lot of ability to avoid the hook),Winston (can close the distance fast), widowmaker ( basically one shots him)
Pharah-
The rocket aoe and ability to shoot over terrain makes her able to clear out clumped enemies or heroes that rely on shields.
Attrib:+AOE on rocket, Ultimate can clear a section quickly –exposed to a lot of heroes in the air, not very effective at close range.
+Reinhart (Burst down shields), Lucio (can hit him even though he is mobile),Bastion(3 shots him quickly), Torbjorn (kills turret quickly)
-Widowmaker (snipe her quickly), Roadhog(hooks her relatively easily, heals from the rockets), Tracer (rockets almost never hit her), reaper (can push in quickly and avoid damage)
Reaper-
Can move a short distance without getting hit. Has very high dps at close range, maybe best dps at close range in the game.
Attrib:+quick reload time, easily disengages when making mistakes, one of the strongest ultimates in the game –runs slow, not good at range,
+Bastion (can flank, phase through), Lucio (shoots in a region), Winston (can avoid him and rarely misses him)
-Reinhart(Shield him and charge when damge kicks in),Hanzo(use walls to keep distance, faster), Zarya (Gains a lot of damage from shields on her and an ally)
Solider76-
Multiple types of core DPS and ultimate buffs team. Combos well with nearly every hero. Denies Flanking.
Attrib:+Lots of dps, buffs team pushes into lanes -Not overly specialized not usually getting a large amount of burst damage.
+ Tracer (lots of shots, and has aoe secondary rockets), symmetra (denies turrets, can tank a little bit of damage), junkrat (very hard to hit from junkrat, kills ult well), Genji (denies flanking)
- Roadhog (can heal quickly and hook him), Reinhart (cannot shoot through shields), Widowmaker (cannot flank her and does not tank a lot of shots from her)
Tracer-
Super mobile, moderate dps, very good at flanking where ramps are. Not as good on all maps partcularly ones pushing through a point like temple of anubis, or very open terrain like like lijiang tower.
Attrib:+Extreme mobility, can take over a game – High skill cap, medium damage, depends a lot of map
+Bastion (can flank), junkrat(flanks easily, can avoid grenades), reinhart (flanks)
-Torbjorn(turret targets her well), Mei(aoe damage doesn’t have to hit her) , d.va (lots of shots steady damage), soldier 76/reaper (good at denying her a push down a preferred path)
Defense-
+ Show Spoiler +
Bastion-
Good at sieging into a lane. Useful ultimate that adds a lot of mobility and splash.
Attrib:+Low mobility, lots of dps Great in exposed terrain- not good in covered terrain
+Most tanks, teams that push through chokes with low mobility heroes
-Flanking heroes like genji, tracer; heroes that can shoot him with limited line of sight, such as junkrat, reaper, pharah.
Hanzo-
Good ability to readjust positions. Not a ton of distance, amazing ultimate RYUU GA WAKA TEKI WO KARAU!!
Attrib:+ lots of dps, scales walls, one of the best ultimates in the game - low health, not good at killing tanks.
+Any support
-Any tank particularly roadhog, bastion, torbjorn
Junkrat -
Doesn’t require line of sight and shoots over and round walls and corners. Really good against anything stationary or clumped players pushing together.
Attrib:+shoots fast, lots of damage –Not very good at hitting a mobile target, not much health
+Bastion (DPS down), reinhart (lot of damage to his shield), D.va (can hit her from multiple angles)
-Genji (really hard to hit), lucio (hard to hit), Pharah ( cannot hit her and she can hit him even though he’s hiding around a corner)
Mei -
Buffed to death recently, possible even broken on a lot of the smaller maps. Doesn’t require much aiming skill. Low skill cap.
Attrib:+high dps low aim required – Very little range, usually requires a lot of cover to survive.
+Reinhart (freezes him), Lucio (doesn’t have to aim much, slows him),
- Zarya (can stay at range), widowmaker (can shoot her from afar), reaper (can initiate phase instantly and reposition of caught by her, hanzo (can shoot her through walls or quickly get away)
Torbjorn-
Places turrets that auto aim. Can stay out of the line of sight and still does damage. Low skill cap.
Attrib:+Turrets deploy fast, decent damage – can get shut down hard by a pharah, reaper, or a junkrat.
+ Tracer (Turret auto targets and hits her), Mei (cannot really do much damage to the turret before it kills her), all supports (really good at keeping the masses out of a region of the map.
-Reaper (can phase into behind the turret and quickly kill it), Pharah (3 shots his turret), Junkrat (can shoot over walls killing the turret)
WidowMaker-
One of the best dps heroes at reducing their dps heroes. Her ultimate helps the whole team to understand what is going on in the game and she has a very high skill cap.
Attrib:+High dps, very useful ultimate –flankable, low dps, not good on maps without lots of distance to shoot.
+ Mercy (shuts a mercy down hard), Mei (cannot even get the range), Pharah (being in the air exposes her a lot)
-Torbjorn (his turret auto targest well), tracer (effective at cirumventing), Genji (good at scaling walls to get a flank, hard to hit when close)
Good at sieging into a lane. Useful ultimate that adds a lot of mobility and splash.
Attrib:+Low mobility, lots of dps Great in exposed terrain- not good in covered terrain
+Most tanks, teams that push through chokes with low mobility heroes
-Flanking heroes like genji, tracer; heroes that can shoot him with limited line of sight, such as junkrat, reaper, pharah.
Hanzo-
Good ability to readjust positions. Not a ton of distance, amazing ultimate RYUU GA WAKA TEKI WO KARAU!!
Attrib:+ lots of dps, scales walls, one of the best ultimates in the game - low health, not good at killing tanks.
+Any support
-Any tank particularly roadhog, bastion, torbjorn
Junkrat -
Doesn’t require line of sight and shoots over and round walls and corners. Really good against anything stationary or clumped players pushing together.
Attrib:+shoots fast, lots of damage –Not very good at hitting a mobile target, not much health
+Bastion (DPS down), reinhart (lot of damage to his shield), D.va (can hit her from multiple angles)
-Genji (really hard to hit), lucio (hard to hit), Pharah ( cannot hit her and she can hit him even though he’s hiding around a corner)
Mei -
Buffed to death recently, possible even broken on a lot of the smaller maps. Doesn’t require much aiming skill. Low skill cap.
Attrib:+high dps low aim required – Very little range, usually requires a lot of cover to survive.
+Reinhart (freezes him), Lucio (doesn’t have to aim much, slows him),
- Zarya (can stay at range), widowmaker (can shoot her from afar), reaper (can initiate phase instantly and reposition of caught by her, hanzo (can shoot her through walls or quickly get away)
Torbjorn-
Places turrets that auto aim. Can stay out of the line of sight and still does damage. Low skill cap.
Attrib:+Turrets deploy fast, decent damage – can get shut down hard by a pharah, reaper, or a junkrat.
+ Tracer (Turret auto targets and hits her), Mei (cannot really do much damage to the turret before it kills her), all supports (really good at keeping the masses out of a region of the map.
-Reaper (can phase into behind the turret and quickly kill it), Pharah (3 shots his turret), Junkrat (can shoot over walls killing the turret)
WidowMaker-
One of the best dps heroes at reducing their dps heroes. Her ultimate helps the whole team to understand what is going on in the game and she has a very high skill cap.
Attrib:+High dps, very useful ultimate –flankable, low dps, not good on maps without lots of distance to shoot.
+ Mercy (shuts a mercy down hard), Mei (cannot even get the range), Pharah (being in the air exposes her a lot)
-Torbjorn (his turret auto targest well), tracer (effective at cirumventing), Genji (good at scaling walls to get a flank, hard to hit when close)
Tanks-
+ Show Spoiler +
D.va-
Can funnel a lot of fire power down a lane. Crazy good ultimate at clearing a position, pairs well with most other heroes in the game. Weak to very few compositions. Moves slow while firing and pushes slow. Much better at holding points.
ReinHart-
Least dps out of the tanks, has to push slowly onto a point, can clear a room with ult. Very good on maps with few lanes and hard to push chokes. Much better at pushing objectives.
Roadhog-
Mobile hero. Little dependence on a healer. Aoe hook is very good at catching hard to hit heroes. Ultimate is good at supressing a single spot. Does not hold objectives well. Very good at splitting up a team that is trying to stay grouped up.
Winston-
Very good at holding a point. Shield is great on allies and cannot be flanked with it. Best close range tank for very small places. Ultimate is a little tricky to land. Probably the best tank at carrying a team.
Zarya-
High dps tank, buffs another ally, Most damage out of the tanks. Maybe the weakest tank ultimate. Very good on maps with a lot of lanes and flanking positions.
Can funnel a lot of fire power down a lane. Crazy good ultimate at clearing a position, pairs well with most other heroes in the game. Weak to very few compositions. Moves slow while firing and pushes slow. Much better at holding points.
ReinHart-
Least dps out of the tanks, has to push slowly onto a point, can clear a room with ult. Very good on maps with few lanes and hard to push chokes. Much better at pushing objectives.
Roadhog-
Mobile hero. Little dependence on a healer. Aoe hook is very good at catching hard to hit heroes. Ultimate is good at supressing a single spot. Does not hold objectives well. Very good at splitting up a team that is trying to stay grouped up.
Winston-
Very good at holding a point. Shield is great on allies and cannot be flanked with it. Best close range tank for very small places. Ultimate is a little tricky to land. Probably the best tank at carrying a team.
Zarya-
High dps tank, buffs another ally, Most damage out of the tanks. Maybe the weakest tank ultimate. Very good on maps with a lot of lanes and flanking positions.
Support-
+ Show Spoiler +
Lucio-
Decent aoe damage, buffs team damage and speed, best opening hero for a team racing to a position. Lots of mobility tricks that make him hard to master. One of the easiest and most intuitive healers, but is limited by line of sight making him good for teams that group up hard.
Mercy-
Best healer, can stay in battle without being in line of sight. Doesn’t pair well with a lot of the mobile heroes, can easily heal heroes on the high ground, making flaking heroes much stronger.
Symmetra-
Best support for objectives far away. Turrets give decent dps, but can quickly loose it all at once. Provides teleporter ultimate for quick reinforcing. Not very good at slowing pushes once they have started.
Zenyatta-
Counters very high dps compositions. Can shield and heal a lot of the team at once without line of sight. Can take down a lot of heroes as well. No tank, no win vs Zenyatta.
Decent aoe damage, buffs team damage and speed, best opening hero for a team racing to a position. Lots of mobility tricks that make him hard to master. One of the easiest and most intuitive healers, but is limited by line of sight making him good for teams that group up hard.
Mercy-
Best healer, can stay in battle without being in line of sight. Doesn’t pair well with a lot of the mobile heroes, can easily heal heroes on the high ground, making flaking heroes much stronger.
Symmetra-
Best support for objectives far away. Turrets give decent dps, but can quickly loose it all at once. Provides teleporter ultimate for quick reinforcing. Not very good at slowing pushes once they have started.
Zenyatta-
Counters very high dps compositions. Can shield and heal a lot of the team at once without line of sight. Can take down a lot of heroes as well. No tank, no win vs Zenyatta.
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Cores(tanks and supports) vs dps(offense and defense)-
A lot of the dps oriented heroes can kill a large group of heroes due to the large damage they output in a very short period of time. These heroes often have larger flaws, such as bastion, widow maker, and junkrat. Your core is generally the best heroes to change out, which is usually a lower dps compositions with less flaws and dependencies on their ultimate. Due to this concept of the low dps generally being better to switch out I'll compare a few sets of 3 core heroes to explain what they work with together along with their advantages and disadvantages.
Core compositions and their benefits on maps.
Reinhart, Mercy*, Reaper-
+Choke pushing, close range, survivability, high lane presence
- low dps, loses to flanks,
*notice that with mercy, since she has low dps a more dps oriented support is used. Symmetra far from the point, and zanyatta against tankless teams.
Zarya, lucio, D.va-
+Very good clearing chokeless composition. Lots of dps and healing. Can hold a point well. Good against heroes that have splash damage.
-can be singled out by strong widow makers and maps with funnels. The ultimates are a bit weak, not good for clearing an objective all at once.
Roadhog, zenyatta, mei
+ The mei can stay in cover and poke out on whatever the roadhog pulls. The zenyatta can shield him and increase the damage on the mei. Its good for a map with a little side building and an open region around it.
- Does not do well pushing onto a point. Doesn’t do well transitioning between places that don’t have much cover.
Some generally not good core compositions-
Zarya, Mercy, Zarya-
The mercy needs a bit of protections, but the zarya's both cast shields on each other that boost their damage. In general it will be hard to keep the mercy alive with this composition making her effectively useless. Weak ultimates.
Lucio, Mei, D.va-
This composition in general is bad because most of the maps have an angle where a sniper or bastion can pick these off. The lack the power to shield and dies to aoe ultimates. It will be hard to keep them together and not die. Weak ultimates that don’t pair together.
Symmetra, Winston, Pharah-
Symmetra and pharah are not good at pushing, your core will spread out quite a bit and be picked off. The dps from the pharah is not enough and winston will be jumping around too much that their core and just push your core. Also its hard to have a shot caller in this composition. It leads a lot to snowballing from the enemy team. Ultimates do not synergize well.
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Closing thoughts-
Hopefully this guide will help give ideas as to why you’d choose compositions and the characteristics of the maps that makes them solid. I did not include all the permutations of compositions, but rather general principles and some examples to help players understand the hows and whys of Overwatch. Also, I believe it well help players a little to think about how to correctly use a composition that they are running. Thank you for reading this and please leave comments about your favorite compositions that you run on the maps.