She did it constantly while in "Act Freely", which could be a perfectly viable option when you wanted your party members with healing spells to heal and attack at a similar ratio. The fact that you could not choose that option for Mitsuru only shows the AI was crap. Other, more restrictive tactics are not really AI, you were basically forcing your teammates to do just one thing. And even then, there was plenty of room for them to screw up (e.g., using a diarahan when a character was losing only 5% of his life, choosing a low-level heal spell when they had plenty of SP, casting an all-team support spell when only one of the team members was missing that buff, even when they had the one-character version...I could go on)
Paraphrasing you, the fact that you defend Persona 3's AI shows you don't understand what good AI means.