She ditches Sylvanas, her race and her continent to join Good Queen Calia, so I'm home free. You can send me a shirt for my gift of prophecy though, I'll appreciate it.
@
Tenebra the War Criminal
We have nearly all story material already available and confidently say that the Horde and Alliance play next to zero part in resolving the problem. It's all down to Magni and the titan stuff. But let's ignore that presentation and just accept that their unity is very essential for fighting N'zoth. Even then, that'd have no weight on the Alliance going on to extract costs after the war effort rather than just taking the enemy's word for it, an enemy that as already mentioned, only ditched the war they were waging because of Sylvanas's attitude towards the Horde personally, not a disagreement with her war goals.
As for characters calling out Anduin, Sylvanas does not do so, this is treated as Sylvanas tricking Saurfang and we know for a fact that every aspect of Sylvanas' plan is wrong, down to her not believing in it and just wanting to do it to off as much people as possible. They assume Anduin isn't a messiah and pay the price. Saurfang and Sylvanas operate on the basis that the Alliance have far more depth than they actually do, and that's why they fail.