Of course they are chaos, not undead, which probably makes sense from a WFB perspective. They would make sense in a Beastman army for sure. I think the upgrade to 4+ regen is not bad, but can be defeated by flaming ... I might be inclined to do take ASF on them..
These are pretty sweet models. I could see them being used in a V. C. army as Crypt Horrors (I think that's what they're called), in a very feral themed army; lots of ghouls, wolves, Varghulfs, etc. Either way, great sculpts.