I don't like/trust Vol'jin never have never will. They have shoe horned him as a character since Classic WoW. Garrosh was once a decent character and while his Warchief reign has been short, he's made a much larger ripple then the useless Thrall who did nothing but apologize every time the horde did something the alliance disliked.
The only Horde faction leaders I like are Lor'Themar and Sylvannas, I don't know enough about Baine but if he's anything like his old man then I'll add him to my list of awesome faction leaders.
I side with Garrosh, he didn't do anything wrong his methods might have been nasty but what he did was within his power and in order to strengthen the horde. Remember that Theramore was a fairly large alliance base that was very close to Orgrimmar and an actual threat. If Garrosh is going to die he needs to die at the hands of the alliance not at the hands of Vol'jin i'll be super pissed if they give that douche the glory. Then again I wouldn't be surprised since they totally shafted Sylvannas in Wotlk when they didn't let her take down Arthas. Out of all the faction leaders in Azeroth Sylvannas was the one that deserved the kill the most.