I just fixed it
This opens up to potentially new stuff perhaps enemies and lore that are on a multiverse level think of the Living tribunal, Thanos, Eternity, the Celestials, Galactus, Oblivion, those kind of things.
Now that we know theres 2 different universes together, this creates 2x the amount of burning legion enemies that we need to defeat, 2x the amount of old gods, 2x the amount of titans, and 2x the amount of bad guys overall.
K , I re-edited it again, since Garrosh was not in that alternate universe for 30 years, but had to take some time to form the Iron Horde.