AI do not seem to be reacting to gunshots even at close range. You can fire a loud weapon all around them and get no reaction. They only notice that they are being shot at when they see a tracer round, or a bullet impact land in their vision. This happens regardless of skill level set on the AI. (Tested with default 50% skill and 100%, no change).
This is very bad because it is causing AI to not react realistically to being shot at. They don't seem to notice when you kill others around them either (unless they actually see it). They seem to be completely deaf.