Something must be off with the Z axis for the mobs in Dain's room. Last night Dain and his guards come running down. Today I was summoned up to their room.
I think this is more likely that you damaged one of the named in there whilst pulling (there's quite a few in there with low hit points), so a riposte or something would be enough to make them start summoning. I just tried myself and it was fine unless I damaged one of them.
Nah, there is something definitely wrong with the axis. Several times I have been on the second floor and pulled the councilors from their chambers and somehow aggroed Dain. When I'm pulling the chambers it only happens when I try and pull the whole hallway. If I pull each set of rooms individually I get no 3rd floor aggro. Happens on both the left and right side of the second floor.