I know for a fact Paladins can solo it, and I'm fairly sure that I've heard of Priests, Mages, and Druids doing so as well. And this is just at 85.
By the time we get to the end of MoP, I'm willing to bet that Ashes will be just as common as the Blue Proto-Drake is now, especially if it does end up on the Black Market every now and then.
Mind you, I don't actually care that it's gonna be come common, I'm just saying is all.