My bro Illidan once said; YOU ARE NOT PREPARED!
and damn was he right, if they made a legion expansion just after Deathwing, we wouldn't be. The wrathion questline, the titan lore and the old god lore we got from pandaria have made the way for the legion's return, we know more about the titans & old gods, giving us a fighting chance to mayhaps contact them, (if they're still out there) should Sargeras himself arrive.
And wrathion, like him or not, is looking out to be the spearhead against the legions return, he is doing what he can to prepare Azeroth... in his own chaotic and slightly manipulative way..