Most tactics games I've played, enemies don't really have synergy either. It's either
1. They wait if you're too far, or
2. They just start moving towards you if you're out of range
3. They just start attacking you if you're in range
Nothing too special. Enemies aren't re-grouping for better heals, or re-positioning themselves to pick off actors.
So I think for AI plugins, it'd probably be ok to just start with a simple one that let's you add conditions to each action, and if it's not met, see if the next one is available.
Pretty much all of your conditions will probably be "is any target in range" so that might be provided as a "global" action condition so you don't need to write it again and again. Then you might have a condition that prioritizes weak targets, or "highest number of targets" in the case of AOE.
And then maybe we'll figure out how to create rules that will allow enemies to synergize better. Run back if they stray too far from allies, etc.