To Garrosh, fear (the very fear that once held him back) is the real enemy. The Horde can fear nothing, because it is what freed him from his fear in the first place. Garrosh embraces the Horde because it was the Horde that helped rid him of his terror of becoming like his father. Now, he seeks absolutely nothing more than to be exactly like his father , to the point where even Saurfang comments on how like Grom he is. What Saurfang sees as a cautionary warning - "You're too reckless and impatient, too eager to risk war without even considering the costs" comes to Garrosh's ears as the highest possible praise. After all, his father is savior of the orcs! His father is a great hero! No longer does Garrosh have to stand by a fire, torn by doubts that his will be the hand that dooms the orcs as his father... no, everything his father did turned out to be the right thing to do. It's good to be a Hellscream and act as a Hellscream acts.

Thrall and Drek'Thar have no one to blame for this but themselves, because when they got to Nagrand and found Garrosh paralyzed by indecision their choice was to remove that indecision by making Grom an idealized hero and completely glossing over Garrosh's very real concerns. The fact is, Garrosh is a young orc with a young orc's tendency to go to extremes, and they completely failed to convey any of the complexities of Grom's life to the young orc. His regret, his understanding that he had been duped, his constant battle with the blood haze, his failures and mistakes, the context that made his last heroic stand against Mannoroth a heroic objective correlative. In slaying Mannoroth, the demon lord, Grommash actually slew his own demons as well, but without the context of his own struggles and the suffering his recklessness caused him, the story loses its cautionary bite and Grom is elevated to a cartoonish idol. And that's exactly who Garrosh is trying to be, the cartoon of Grom that Thrall inadvertently created for him at Garadar.

So now Garrosh is pefectly poised to repeat his father's mistakes, because they've been changed into virtues in his eyes. He must find Thrall paradoxical and frustrating, as the older orc has gone from the one who brought him this new understanding and a new world to belong in to a constant irritant trying to get him to stop behaving like a Hellscream. No wonder the two are at constant loggerheads: Thrall wants Garrosh to be his father, and so does Garrosh, but Thrall wants Grom as he remembers him and Garrosh has no idea who that orc is. This all stems from Thrall's tendency to make demigods of the leaders of the old Horde that he met at the end of their lives, like Doomhammer. The Grom Thrall knew was not the one Garrosh would have known. How could he have been?

It makes me wonder what would have happened if Thrall had sent Saurfang as his emissary. At any rate, however, considering what he's been exposed to Garrosh has managed to become exactly what he believes is expected of him in a very short time. He's gone from a sullen adolescent (I have no idea how old Garrosh actually is, mind you) to a warrior capable of giving Thrall a fight and staring Saurfang in the face without a trace of fear. I'd like very much to see a Saurfang/Garrosh duel... if Garrosh won, it would fuel his already aggressive stance even further. And frankly, it might be a good thing for the Horde overall.

The Horde is, and has always been, at a pivot. Thrall's decision to make heroes of members of the old Horde has in effect meant that his government could never disavow their actions, and as a result, can never find peace with the Alliance who remembers them as blood crazed berserkers who poured into Azeroth through the Dark Portal and made common cause with cannibals and lunatics who explode everything in sight. Now, if the rumors are true, rather than a mystic, the Horde will finally have a leader who will fully embrace the warrior ethos of the old Horde and in so doing, bring it home for everyone involved. Frankly, any movement on this part is forward movement, rather than Thrall's hesitant, half-hearted attempts at detente. Perhaps the war needs to burst into full fire once and for all, and if so, Garrosh could be the best possible leader for the Horde, one who truly believes in his people and their righteousness without ambiguity or doubt.

Ironic that it took Thrall, son of Durotan, to give Garrosh, son of Grommash freedom from his doubt and uncertainty, thus making him what he is today.

I feel bad for Garrosh, because I'm pretty sure Cataclysm will be his high point. From there, he'll have to learn, the way his father did, that bloodlust has costs. It seems a shame that the sins of the father are to be visited upon the son who was the most afraid of them.

Edited to Add: Wow, lot of interesting comments already. And while I don't think I possibly can answer all or even most of them, that doesn't mean I don't see your points, especially the ones about how Garrosh seems ungrateful or unrealistic and about how the Thrall/Garrosh fight can be seen differently than how I saw it. There may be enough in what you're all saying for another look into Garrosh in the future.