I've registered because I'm curious to know what's going on under the hood, and on reddit they weren't really helpful.
So, I only played the original games, and it was long ago. I downloaded the 1.5 r6 beta and I'm seeing behaviors with the AI that are at the very least weird.
I simply started story mode, veteran difficulty and went in Cordon at the first bandit camp. I sneaked around, leaned from the wall and killed a bandit near a fire. Only to move a bit further and notice that the other two were still standing there doing nothing at all, even if I killed their companion right in front of them.
Then I restarted, this time at "master" difficulty. I tried to shoot once while I was still completely behind the wall, and all three bandits were properly alerted and came to me. So they indeed could hear the sound, this time.
But then I bumped into another similar problem:
I was right next to this guy and shooting just above his head. He just stood there, once again the AI being completely oblivious to sound. That guy only started to react again and shoot at me when I moved within his (very narrow) field of view.
So what's the problem here? Is it some bug with the new beta? These bandits just seem to lose completely their hearing. And it's erratic because sometimes it seems to work and sometimes it completely breaks apart.
If you want I could even post the savegame, but I literally just started the game and went to that bandit camp, no mods at all installed.