Some may say that instead, it would be nice (especially for beginners) to have simply listed all abilities that all selected units may cast, in this case just pressing B for Blink, F for Field, and T for Storm, instead of having to tab among them. However I see two downsides.
First, many players use the same hotkey for the abilities.
Secondly, my proposition is better, because some units share the same ability. For example, in LotV it would still be necessary to have a separate hotkey for Lurkers, because their burrow ability is the same as for other units. Being able to have them still grouped with Hydras, while just highlighting them to perform the next action, likely burrow, would make things easier.
Moreover, it might be good to make “highlight groups,” either predefined, or by quantile - i.e if it was alt 1-4, alt-1 in this mentioned scenario would select first 25% of the selection - 6 zealots. It would be then possible to have this one large group of selected units, with being able to send portions in different direction, i.e for Zergling surrounds.