There are plenty of times where you watch one of the AI characters on your team use up their skills on low-level characters or at otherwise less than ideal times, making those key skills unavailable when a boss appears or when the skill would be of more use.
One current solution is to babysit key heroes by playing as them and thereby ensure their ability isn’t used prematurely. Obviously this means you’re not controlling a character you want (eg matador so you can pick off support people to shield up) and this strategy is also inherently unscalable since only one hero can be controlled at a time.
The solution I would put forward is: just like the ‘autoplay’ toggles whether the AI controls the current hero, an ‘autoability’ toggle would control whether the abilities of heroes are auto-used by the AI or whether active abilities are paused for AI-controlled heroes. The benefit would be that you can click of auto abilities when a stage is almost cleared and then later, when you need to turn back on the heat, toggle it back on and those saved abilities will now be used at a time they are more well utilized.