We all complain about Henchmen. Being a programmer myself, I know the challenge of creating a well-balanced AI. However, I think one small enhancement could be made that would drastically reduce PvE frustrations.
Henchmen need a "regroup" command. You would click a button on-screen, and the Henchmen would run to your position AND DISREGUARD EVERYTHING ELSE. They would not stop to fight, cast spells, or anything else. They would just do their best to regroup around your position.
After they arrived, they would continue to fight as normal. This addition would not be that hard to implement, and would greatly enhance PvE when Henchies are involved. What does everyone think?