I dont think anyone out there would mind if the AI would get a big rework.

• Shooting throw walls
• One hit killing in a split second
• twitchy suddenly change of walking derections
• no foot step sounds
• bot like movement

Thats not realy challenging more like frustrating. They dont even try to stay alive. Make there movemend more human. Turn down there random god aim and maybe give them some team tactics. There are games out there with AI that are doing some cool shit. (SniperElite, PayDay2,MGS5) There is so much inspiration out there to copy of from.

Coop is the best thing about this game, now lets make it even better.