I’m certainly no combat expert but I would think that its because you are fighting zombies that dodging can be so effective. Zombies are exceedingly stupid, almost every media I have ever seen that portrays zombies has the correct way to fight them being exploiting their predictable attack patterns. We’re not talking about dodging several fighters who understand the principles of flanking. Or even animals who might instinctively attack from blindspots and the like. We’re talking about simple, slow lunges where they trip over their own feet more often than not.
My understanding is limited but I would like to think that even unskilled fighters would have trouble coordinating, simply put its easy to get in eachother’s way. But even more so with zombies. Usually zombies aren’t just getting in eachother’s way but they actively pull and climb over one another in their desperate scramble to bite a human. To the point where rather than calling it an attack its more like a wave of flesh when zombies gather. To that end, zombies should gain bonuses in a horde as their sheer mass overwhelms conventional fighting methods but in small groups they should hamper eachother as they struggle to form the most basic coordination.
Ofcourse it may be possible for some zombies to be reasonably intelligent (at least as intelligent as an animal) but the average zombie is definitely not.
Dodging being restricted against any other attacker working in tandem I would be ok with, especially with the dodge modifier from open spaces suggested earlier. But zombies are nigh incapable of working together and its only when they reach a critical mass can they form a vague semblance of coordination.
Although that is all besides the point I just wanted to ground the discussion in the game’s core engagement. This isn’t an MMA simulator but the key point of the game is fighting incredibly unskilled enemies. The realism argument is used because realism tends to be enjoyable but at the end of the day the game balance should be what gameplay is most enjoyable and encouraging diverse tactics. I’m not good enough at the game to even try to discuss game balance. But zombies have had their feeling changed greatly over the years and my opinion is that they should be given their own balance in regards to dodging and group fighting thats separate from other enemies to preserve the feeling of fighting a near mindless horde.
TLDR: One should fight a horde of zombies much, much differently compared to a pack of wolves or to a group of unskilled thugs or even to a well coordinated team of fighters.