We have had multiple instances of this happening in game already. Velen's vision isn't new. Tirion vs the Lich King in wrath. Khadgar and the Legion. Bran Bronzebeard and Ulduar. Thrall vs Deathwing. There are many instances where a certain leader is the face of the coalition and Anduin vs the Void is not "unity for everyone." It IS implausible because the developers themselves don't want it to be a thing.