Velen hands down, hes too mighty. Through foresight he would already know this battle was coming anyway, and would have some well thought out plan to deal with it. The only other leader that comes close to his power, would be the new total shaman Thrall. But i doubt even he would have enough, Velen is just immortal (his age isnt an issue) and too expierienced. Thralls not even in the poll anyway, even though he still is a world leader(Earthen Ring and every horde leader would still listen to him).
So yah Velen got my vote.
Edit: aww poor Baine still zero votes. Love the character, hes just outclassed here