I wonder if it would be feasible for SE to create tank/healer AIs that could be added to a pt after something like 20 mintues have passed trying to get in. They'd need to have a script tailored to every specific boss and dungeon leg. Movement would be a whole other problem, since you usually want the tank at the front of the pack(might have to make them phantoms or something that spawn when you aggro, and despawn once the mobs are gone). Probably way too complicated to get working well, though.