This is what I referred to as Doom 3 monster closets, and it also pisses me off. It's cheap as hell.
Each time you stumble upon a circular-ish area that has a bunch of ladders to it, you can be sure as hell that the moment you walk into the middle of it, shit will pop up all around in very conveniently placed tacticool positions and start pummeling you from high ground.
By this point in coop each time we approach sth like this, someone says "this looks like trubble", followed by "battle stations", and getting everyone teleported to the vantage points before the inevitable monster closet is opened and Swen appears behind you irl to slap you in the butt while yelling "GOTCHA, BET YOU DIDN'T EXPECT THAT!"
Hurr durr great design right there.