First of all he says he challenged Garrosh alone and doesn't recognize my character as having helped him. Which would mean he would have died up there.
He says he's concerned that Wrathion thinks human life is expendable. I'm not sure why he specified human.
And lastly, he was apparently healed by pandaren mistweavers. So not only does Velen not show up in game, he doesn't show up in lore either.