OP, you are wrong in so many levels.
I'm an Orc and i love Thrall. Orcs love Thrall, Thrall took use from slavery and turned us into one of the two dominating factions in Azeroth.
Garrosh is loved, yes, but less than Thrall.
The alliance doesnt need to love the Horde leader....
Thrall didnt ignore Vol'jin warnings, neither he ignored Cairne's. he though that Cairne's and Vol'jin advice would be enough to offset Garrosh's idiotic behaviour. It wasnt, it was a mistake from Thrall, but Vol'jin (as well as Cairne) is one of Thralls bes friends and most trustfull advisors.
So after Garrosh kills one of his friends and now threatens another one, is makes an absolute sense that Thrall decides to oppose Garrosh.
The story can progress fine with Thrall, and no you get it wrong. The story is not about us, Tirion and such are not there to witness us.
The story is about them, we are just nameless adventurers that help THEM, not the other way around.
The story doesnt make sense with Thrall dead. WoW story needs Thrall, it wont actualyl make sense without him.
The horde is getting our from a tiranny, the horde society need to make sure the next Warchief is a good one, we cant withstand another tyrant. So the next Warchief need to be one that without any doubt will not be a tyrant. The ONLY one that fills that spot is Thrall.
We cant know how Saurfang or any other candidate will act given enough power, but we know how Thrall will.
I understand that you as an alliance dont want us to have a good leader, but we deserve one, especially after this two expansion of having this idiot in charge.
We need Thrall back.
We need our Warchief back.
Chris promised we would get it, and we trust Chris.
Thunder is coming....
Thrall is the modern Horde and atm the horde under Garrosh is just a reversion to the Horde of the 1st and 2nd wars.
Garrosh's horde doesn't allow for for meaningful allies, while Thralls Horde thrives on outcast races banding together.
People claim that Thrall doesnt care or understand his people and that he should of stood up for them more, however Thrall's actions were about peace. With peace you don't see the waste of lives and resources or the straining of alliances among your faction that you do in war.
Besides if any leader should be killed of it is Malfurion for turning down the gift of the return of the Night elves immortality without the concent or knowledge of his people and the disregard and disrespect for his wife who is true leader of the Night elves