Also, in "The Vault", sometimes one monster in a horde stop attacking when it is near a corner.
This is an issue I've found throughout all dungeons and whenever there's a wall around. I've noticed my char stops fighting and loses target focus. Strangely enough, mobs don't - if they've already attacked you, will keep hitting you, while your toon won't fight back. And sometimes it's the other way around...
- D4VYJONES likes this