Attached pic with 2013-12-01 shows a cluster of AI jammed up into an open intersection. The main obstruction is a dead body, which is now creating a massive AI pathing cluster-f right out in the open.
ThisDoorScaresUs.jpg Shows a gap in fortifications that AI/players can easily fit through being "blocked" by a dead body. At this point in the mission, all AI refuse to move through the opening. Clearly there is more than enough room between obstacles, and the human players have no issues at all moving through the gap.