We already know that the expansion ends with both sides uniting to bring down Garrosh. We can't say for sure but that sounds a lot like them putting aside their differences to deal with a real threat. It's not that 'war' is the enemy, it's that 'Garrosh' is the enemy. He won't listen to reason and the Alliance has to fight the Horde or be wiped out by it. It's not really a two sided story morality wise, though the purge of dalaran adds some moral gray to alliance.