Of course, FNP still makes them an excellent fire soak -- they'll eat anything under S6, regardless of AP, without blinking an eye. And, unless you really have nothing less threatening in your list, I'd imagine that not that many people are going to throw power weapons at these guys, so that's actually not such a big deal.
Now -- if you hide a nasty Asp Champ in there (maybe even model him as an uber-zombie? :-) ) and give him, say, Lightning Claws... maybe they'd bother bringing the pain. But really, which armies can field substantial numbers of power weapons (parenthetical: that are cheap enough that you'd bother throwing them at zombies) anyhow?
Hmmm... the more I think about it, the more I want some zombies...