Hi guys, Im a Lore lover and im new to this group.
Technically Thrall was holding the Horde together until Garrosh came along. Thrall had a peaceful way of leading the Horde, making allies unless they were hostile, he was even willing to ally with the Night Elves and the Humans at one time, he helped the Darkspear Tribe, Guided the Taurens through Centaurs and Harpies. Grommash was like a brother to him and with that love he trusted Garrosh, he is literally the good guy in WoW Lore, then after Garrosh got into high places he f***ed up everything.
He was uninfected with Demon Blood as far as I know but he was a reckless and savage leader, fought alot and broke Thrall's order, only because Thrall cared for him like he was Grom was the reason all that was looked over. Then Vol'Jin didnt like his savage nature, preferring Thrall's kind ways, neither did Cairne, who fought for a way like Thrall's rule died by Garrosh's hand. ( I liked Cairne ;( ) now the Horde is falling apart while Thrall is off trying to literally save the world.
Thrall aint no Saint, he has killed before and he is not entirely pure evil, but he didnt screw everything up like Garrosh. Thrall's my second favorite living character in the WoW Universe, Blizzard screwed some stuff up.
Also on a last note the Orcs were peaceful and even took the Dranai in before Magtheridon got Demon Blood into their system, then the rampaging and destructive Horde was created, not Ner'zul's fault for becoming the Lich King and destroying everything, most of you would have done the same thing if you were being tortured and the only way out is to become an all powerful but immobile armor set.