Use a different script

My Mage uses Ranged, somehow I have not this issue. But if your character interrupts his casting to shoot, then use Passive.

For Bard i used Bard-controlled
For Thief - Thief Scout to keep it always in shadow, still very messy
For Cleric - Passive or Druid Offensive/Defensive - this way Cleric uses all his heal spells on party, that very hard to do manually

I usually remove scripts and turn off the Party AI...it's an old habit and not terribly realistic but does prevent a lot of stupid blunders by your party.