It goes without saying the Old Horde with their raping (literally; they raped Draenei), pillaging, and genocide against all life was pretty much the Locust Horde from Gears. So for a brief history lesson, that much is known.
When Thrall was put in charge, he steered it down the good path. Apart from Varian, Alliance leaders liked him even! But his approval rating wasn't that high in the Horde itself, with many Orc dissenters hating his pacifist ways and the Forsaken being upset he watches them.
So I can see why he had to leave when Deathwing rampaged. But it ALL WENT DOWNHILL AFTER. Garrosh LITERALLY turned the Horde back into the Old Horde. But Thrall doesn't do anything about him, claiming the Horde now has its own responsibilities. Only after he threatens to end the universe does Thrall intervene. When Garrosh tells Thrall he ditched him into a role he was unsuited for, he says that's not really his fault and murders him.
And now look at Sylvanas!
While Thrall has decided to take serious action at last and times are nice again, EVERY ITERATION OF THE HORDE IS CHAOTIC EVIL WITHOUT HIM. It just paints a sinister light on the Horde as a whole and I'm wondering if that's really his fault. He is pretty much all that ever holds it together and it's crazy to think what the hell would happen if he died.