My solution is simple, a crossbow trap on the wall in the hallway on the opposite side of the door, triggered by stepping on the plate on the room side of the door. Everyone in the room is out of it's line of sight and closing the door blocks it entirely, but anyone left in the outside hallway... well they are good targets... or hell flank the door with 2 of them and put one on the far side of the door.. If anyone attacks one or tries to disarm it that triggers them to start... and the plate on the other side of the door.
That will get everyone into the room fast =)
That will get everyone into the room fast =)