I think one of the current biggest issues with zombies is moreso uncertainty than straight combat statistics.
Players have been defending against Xenomorphs - speedy, melee-orientated threats - for years. We know what kills Xenos, and how they make more of them.
As such, I think taking some notes from our alien friends would be a good call:
Marines can be hugged on the frontline, and recovered and treated without too much hastle, as there are a few ways to slow larva grown and frontline hugs are usually up to chance: A lucky hugger, a well-placed egg, or a ballsy Carrier. All of these threats can be shot at or burned, however.
If a hive wants a safe, speedy burst: they need to take-down a marines and get them back to the hive, which speeds the bursting process up.
Similarly, I’m not sure if catching a grazing slash against your elbow being a death sentence is necessarily rewarding and feels rather cheap.
As such, I feel that slashes should have a low infection chance, and that their greatest utility should be slowing people and adding-on wounds. However, zombies should have a bite ability that is a wind-up, and guaranteed to do heavy damage and apply an advanced stage of infection. This would mean, ideally, that combat becomes less a matter of lucky scratches from across cadelines, and moreso represent common portrayals of zombies dragging someone down into a horde, feasting on them, and the victim raising up soon after. Additionally, it would help to swell the zombie ranks for gaining confirmed kills, whereas a few walking around to slash bodies to rise in a few minutes is less engaging and thematic.
Bonus points if the bite ability heals the zombie doing it.
A complaint I often see about zombies at present is that once they get started, it is difficult to stop them on account of how hard it is to ensure they are put-down properly and consistently.
Due to this, I believe they should all have reduced limb health, but none of the pain or bleeding that would cripple a mortal character. The intention here is that zombies could be delimbed under heavy fire, potentially leading to crawlers with no legs or glorified meat shields with no arms, but may still be able to infect downed marines through a bite. Also, of course: more dependable decapitations.
Overall, I believe that both of these changes would
- Reduce aggravation resulting from one lucky scratch ending your round.
- Aid how fast zombies can raise corpses (or very unlucky marines)
- Give marines a way to apply attrition and confirm kills consistently, and promote zombie swarming.