I've seen another bug related to AI and targeting involving two players being in different "dungeons" on the same map. I have one good example off hand.
I dont have access to the game right now for cords, but if you go to the ladder to the second floor of the big dragon cave behind Midgard AND someone is in the Dire Cave on Valour map at the same time, the Gold dragon, blue dragon and baby dragon will never aggro anything until attacked. They aren't going after the person in the Dire cave, they just path as expected for non-aggroed monsters. This keeps happening after respawn of the dragons as well.
Pennywise - 7 Seconds - Fugazi - Husker Du