You may want to fix this:
http://imageshack.us/f/194/exploitn.png/
I was able to bring three of these statues into the room by myself during a solo mission, quite absentmindedly without really trying. I think if i were so inclined, i could have brought all four statues into the room to block the spawn gates. All a matter of arranging them on the party button before you step on it.
Four people would be able to bring them in with little effort.
I was so distracted while trying to arrange the statues in front of the bombie gate that i got myself killed :P
Oh well...
And here I was using the totems to block the spawns...
Also, you only need 3 for the last room
Edit: Oh, you're talking about the upper left room... wouldn't it be difficult to effectively block all 4 bombie spawns with only 4 statues? I wouldn't be bothered.