In my opinion, WoD is exactly why Vol'jin or any troll or any other race for that matter should have never become warchief of the horde.
It's obvious the next expansion will be orc lore heavy from the horde side and I feel Vol'jin just doesn't fit in all of this. What's his stake in all this?
Can you imagine someone introducing Vol'jin as warchief of the horde to legendary orcs such as Grom, Durotan, Doomhammer, etc.? They would laugh their ass off.
Of course Blizz will try to explain it away but I think no matter how they spin it they made a huge blunder there.