I also think the zombies move way too fast. With the increase in zombie population, and the fact that they NEVER lose you once they "hear" you (even if you moved into a hidden spot immediately after making a noise with no zombies in line of sight), they should move slower. Having every zombie in a 100yard radius running STRAIGHT to you after making a noisy mistake breaks the immersion greatly imo. I also have a feeling that if they didn't move so fast the pathing wouldn't glitch out quite so bad, but that is just a gut instinct.