Yeah his flaws and mistakes make him interesting, but are also the reasons for which is the villain now. Not because people cannot commit mistakes, but because he doesn't take responsiblity of no one of his mistakes, for him everything is necessary, justifable and good, and the line in which he would finally realise that maybe not everything of what he did was the best of the best, seems still unknown.
But that would have been out of character. You want the standard "evil" guy because you cannot see anything else apart the "i want more power because i love to be a god, i want to destroy the world and kill anyone because i like killing" being bad and simply too dangerous for let it go. Garrosh is not evil, he's reckless and dangerous, like his father, he would easily cause another Cataclysm and blow up half of the planet if the thing would support his goals. But hey, he don't say "i'm a baddie, me random smash", so who cares, leave him alone.If Blizzard wanted me to hate Garrosh they should've been more clear on his motives. They should've let Garrosh kill children and betray his own faction and outright state his desire to become some sort of God
The bombing of Theramore showed that he was eager to become a thief (by stealing the Focusing Iris) and fight (not much fight, just destroy) his enemy as a coward if the thing was necessary for further his great plans of Kalimdor's domination. But the destruction of the Vale being "quite normal" in war is the top, the Vale was not in the center of the conflit between Alliance and Horde, he stirred that gigantic mess there only because he dug where he shouldn't have dig, all for obtain his precious new (and dangerous) toy, giving a fuck about the consequences, like he never do. If you can't see this as wrong, it's nothing but your personal taste, but you cannot blame Blizzard for that.Now I don't exactly see the bombing of Theramore or the destruction of the vale as a reason to kill him, it's quite normal in war.