The Horde doesn't need to redeem itself. At best some members need to redeem themselves for their treason, but most of the traitors like Baine and Saurfang are way beyond that at this point. Redeem itself in the eyes of Alliance, as it's what Blizzard would understand by Horde's redemption? Fuck no. Alliance isn't the Horde's overlord or even a partner. No one in the Horde should give a shit whether or not they get a redemption seal of approval from Genn or Tyrande.
Blizzard should take a note from SW:TOR here. Even light side Sith aren't buddy buddy with the Jedi or using the same morality as them. The light side Sith oppose the aspects of Sith culture they find to be undesirable
from the perspective of the Sith Empire. Like the constant infighting that's pretty much institutional or stratified society. They oppose them because they make the Empire lose wars in the long term. Not because it makes the Jedi sad. And when they cooperate with the Republic, they do it with things by threatening them with death. Because they are a different culture and light side Sith are not even remotely the same as light side Jedi. Which works pretty much how @
Dagoth Ur said things are supposed to work.
But Blizzard can't comprehend that. For them "the heart of the Horde" like Baine or Saurfang have to be human sycophants that outright seek Anduin's guidance on how to fix the Horde in order to be WoW's version of "light side". Which makes zero sense whatsoever.
The Alliance allowed the Horde to keep its conquest because Alliance was:
1. the aggressor
2. losing the war spectacularly before the Horde started to in-fight and they had to team up with Lol'jin to survive against Garrosh.
Alliance wasn't in position to demand anything.