Camelot Castle Dungeon in particular.
Here is the problem:
Faction A logs out in Tarasque room. They have a half dozen engineers with them. Teams are set up and the engineers begin to warp in scores of faction A members. The playfield fills, and is soon overfilled.
Faction B is only able to able to get a handful of members inside the playfield before it is filled by the doings of Faction A. Faction B members die and cannot return to the same playfield because it has reached capacity, as Faction A keeps pulling in reinfocements.
This is not a hypothetical situation. It happened today.
Warping out of the playfield is not an issue, since fleeing is seldom seen as disruptive gameplay.