Originally Posted by
Golden Yak
Like mrsohta said, life and death have been screwed up for a while, possibly as far back as the start of Cataclysm (when Sylvanas suicided for a bit), so anyone who died between then and now is doomed to the Maw, unless some other power has intervened (like Ysera and Elune for example).
As for those from before the whole cycle being messed with, I can't imagine Arthas not showing up in the Maw. Frankly, I lot of the people we as players have killed were pretty bad, so there's probably a lot of them who were going there anyway.
Cairne Bloodhoof died post-Lost King, so he might be doomed, but otherwise I could see him appearing in the nicer zones, maybe Ardenweald or Bastion.