This would be a great, but simple, change to enemy AI. "If Intelligence<10, attack whoever is nearest. If greater than 10, attack the squishiest enemy." Maybe add a couple more conditions so that smarter enemies try to avoid AoOs and/or focus more on getting high ground.
Well, it's a possible example among many, but yeah, that's the sort of nuance I'm talking about.
Another one could be that really stupid enemies don't worry as much about triggering attacks of opportunity.
Or that really smart enemies can make better use of the the environment around them (i.e. "breakables") instead of just attacking.
