I’d update Dread Wastes. Because I have Mantid Bias.
The Wastes are in ruin, first devastated by the Sha and then again during N’zoth’s little stint. Of the major Kypari, only Zan’vess has remained untainted due to it’s distance from the mainland. The swarm is in shambles and Shek’zara had not ruled long enough to produce any known eggs, leaving no future Empress. With no one to lead, the Klaxxi are forced to step in and lead the shattered Mantid.
For the Horde:
Klaxxi’va Vor, recognizing that the Mantid are in a desperate state, attempts to convince the remaining Klaxxi to consider allegiances to other parties to survive, as they did with the Wakener. They refuse, convinced the Old Ones will still return and continue to recklessly embrace its power. So, Vor takes matters into his own hands and sends a call through a mind-controlled Shado Pan to the Wakener to help his people once more (The Shado Pan is released immediately after)
The Horde questline then focuses on assisting Vor, who clues them in to the current state of the Dread Wastes and admits that the Mantid need to change with the world in order to survive. The first batch of quests focus on awakening another batch of Paragons to bolster their chances at securing control from the remaining Klaxxi.
Once a new group of Paragons is assembled, Vor turns his attention to securing the remaining Kypari: Zan’vess and the Void-infected Kor’Vess. Kor’vess is claimed from Klaxxi loyalists, but Zan’vess is held by a surprising force: The Rajani. The Rajani are revealed to be taking advantage of the Swarm’s weakness to begin the final elimination of the Mantid, who are designated as Voidborn. Defeating the Rajani incursion begins to sway the mind of some Mantid, who flock to Vor’s future for the Swarm.
Finally, the final act Vor leads his Swarm to confront the remaining Klaxxi at Klaxxi’vess and defeats them, wresting control of the swarm. This ends with a cutscene of Vor stepping over the Klaxxi’va’s remains and channels his amber magic into the shrine in the center of the base. As he does, the scene shifts to Kor’vess where the void magics are seemingly being expelled by a surge of power within the Kypari. The scene ends with the tree being completely purged of the taint of the Void.
As an epilogue, Vor admits that he could not have done this without the help of the Wakener. With the threat of the Rajani along with their precarious position on Pandaria, Vor declares the Mantid need allies, one they think they can find with the Wakener: The Horde. In a fun last questline, you join Vor and the Paragons in attempting to enter Orgrimmar, only for the Mantid to be attacked by the guards. You battle your way to Grommash Hold, all defeated guards either being encased in amber or simply knocked unconscious. When you arrive, you and Vor enter the hold alone and another cutscene plays. Vor enters the Hold and stands before the new council and states his desire to join forces. The council rebukes him on account of the Mantid’s previous allegiances and demands his departure. Instead, Vor speaks of how the swarm’s greatest heroes stood side by side with the Horde once, though for the wrong reasons, and solemnly admits that the Mantid have been fools. He claims he finally understands that even if the Old Gods were their worship, Azeroth was their home and those gods would have tortured and corrupted it, just as they did the Kypari. Lilian speaks up for them, offering them a chance to redeem themselves. Slowly, other members of the council agree that a second chance should be given, as many of them had been given the same.
Mantid become a playable Horde race and their go to race for Void based expansions. Because I have Mantid Bias.
Alliance would have a separate experience, either in the Southern Dread Wastes or in Kun’lai, revolving around the Rajani, ending with the titanforged Mogu joining the Alliance.