Originally Posted by
Powerogue
Uniting the factions is on Baine, confronting Sylvanas is on Saurfang.
He put his life on the line to save the forsaken Derek from Sylvanas's brainwashing, earning the trust of Jaina. Confronted by Sylvanas, he defended Zelling and took full responsibility, stirring the hearts of everyone present against Sylvanas's tyranny. Faced with something to unite over, Horde and Alliance forces put aside their differences to rescue Baine and confront Sylvanas at Orgrimmar.
Without Baine, Sylvanas would have successfully gotten the factions to consume each other, eradicate hope, and end the world as we know it. Saurfang's rebellion would have ended with him.