I like the idea of the Avatar of Khaine, and would love a reason to run one. However, I've never found a place where I thought an avatar would work better than something else I could spend that 200 points on. Eternal warrior would go a long way towards making him better. It's baffling to me that pheonix lords get eternal warrior, but the avatar of khaine doesn't.
While this is a pretty awesome catch, I don't know that it's enough to warrant the inclusion of an Avatar for me, considering all of the OTHER things that CAN kill an avatar relatively easily. If Guilliman starts showing up in every list, being incredibly strong in the meta or something, I might change my mind, of course.