I had a ton of ideas for how to improve the UI immediately after submitting, yeah. Just made an update trying to make it work while sticking to the resolution.
Breaking up the actions like that doesn't really make sense for what this game is. I want the action economy to be super limited and shared among all actions and all characters on the player's team, so the player only gets to do the 3-4 most important actions they can think of on most turns.
I think the answer is more to have a section with just 2-3 units instead of 5, so players can learn the basic tactics of using shields to waste the boss's time, while using polearms to prevent him from regenerating and punish him if he tries to get past the shield.