It stopped being THE horde and became Garrosh’s horde. That was a set in stone thing to you? I dont think it had to go that way. Blizz just failed the rest of the horde at the time. They meant nothing to the story for whatever reason. Sure you can make sense of it in the way it turned out, but that shouldnt mean it was the only way to go. This is how horde story dies.
I’m not gonna see it the same way you do. All i experienced was watching the horde fall apart for putting Garrosh first for whatever reason. To me, Garrosh’s horde has exhausted its creative potential and begun a terminal decline by introducing an outlandish, desperate element that signals a loss of quality or relevance.