I found the problem, you posted this topic in Day Z Forums > DayZ > Dayz General Discussion instead of DayZ > Technical help Naw just kidding, actually your problem is this "ATI Radeon" Naw just kidding, I actually don't know.
I've continued to play Day Z post 1.7.1.5 and I agree with you to some extent. It's still possible to sneak around but zombie agro seems a little funky, sometimes I can crouch run past stuff point blank and other times they agro from a great distance.