Tbh I got all on passive with defending when attacked and sometimes turn it off

 

Much prefered by me. But even I did notice it few times.

I've seen something similar to your issue, where a team mate just runs off. It normally happens to me when the AI would try to use an ability, like Flames of Devotion or Knockdown, it'd glitch out and just run off in some random direction instead, or sometimes just do a weird stutter step around the area where we're fighting. I just now have my AI on just 'None+Aggressive'  for most of my team, so they'll just auto attack without me having to manage them, and really, most abilities are neglible enough the random use of them by the AI won't matter.

 

As for the AI doing dumb things with the abilites, I see that too, of course, but I think that's just working as intended. It's probably a lot of work to get them actually having something like a 'real' AI, or even set up a Tactics system like DA 1+2 had. (Which 3 mostly got rid of....). The best I think we could hope for is just the ability to go through and click certain abilites that the AI will never use, so when it randomly does something, it at least be the right something.

 

That said, I love the AI, and really makes the game more enjoyable, even in this state. I had quit the game months ago, in large part to how horrible the micro-managment was in this game, to an ungodly degree. The micro is still the same in those tough battles, but now, for most fights I can just let the AI do it's own thing, with me only really needing to manage at most one character.