Doom: Of course the Boomer can vomit or explode on the Survivors while they're in the closet, but it doesn't matter, because they're in the closet. During the event, the zombies are already rushing through the door trying to get to them, and the survivors are all firing in the same direction, wasting absolutely everything. Nothing can get close. There's no angle for the smoker to drag anyone out, either. The only way that I can think of that the closet could be defeated, and this is purely theoretical, is if the Hunter managed to tackle someone while they were reloading or otherwise distracted, and since everybody's so close together the entire party gets Hunter-staggered (there is a brief stun on nearby Survivors when one gets Huntered), during which a second Hunter tackles someone else, and then a Smoker drags a third person out and the Boomer blows chunks on everybody just for good measure. This is purely theoretical and requires tremendous teamwork and timing, but it's a worth a shot. Otherwise, just wait for them to leave the closet and go up to the really, really vulnerable bit of the map after the elevator.