One word: Asians.
One word: Asians.
He was always pretty aggressive; he made his desire to conquer Theramore plain and clear way back in that comic. Even in Cata, The Shattering and Heart of War, where his more sympathetic traits were set up, he was aggressive, reckless and expansionist. He believes the orcs deserve a better quality of life than a desert can offer, and goes to increasingly brutal and questionable lengths to make it happen. He's never gotten along with Vol'jin, and his opinion of the other Horde races has always began and ended with how much use they are to his war machine.
All of that has simply gotten worse over time. His faults have been played up and his redeeming qualities -- admittedly few as they were -- have been stripped away one by one.
It's par for the course of how Blizzard turns lore characters into raid bosses. We've seen it with Fandral, Kael'thas, Illidan, etc.
The horde and alliance war can be so childish, when the kids don't understand the consequences of war, this is what it leads to, tyrant leaders who become the bad guys.
There was a lot of inner struggle for Garrosh. It's unfortunately not very visible in-game (but that's mainly because in MMO's that's a very difficult thing to accomplish simply because of the structure of the game), but we do see it, and we can piece it together from the sections of books pertaining to Garrosh as well as similarly focused aspects of the game. It all comes back to his father (a reoccurring, believable flaw!). He hated his father for becoming ridden with demonic bloodlust, and then learned of the good he did and began to emulate him, without fully understanding what Grom was about. He struggles to find his place in the Horde when he first arrives.
In Cataclysm, we see him struggle with leading the Horde. He sends incompetent generals out to do his work, one disappoints him enough that he goes out to personally kill the guy. In Mists of Pandaria we see he still has a firm grip, perhaps too tight of a grip. He is struggling to control the other leaders of the Horde, threatening that he would kill Lor'Themar for merely disagreeing with him, and even sending an assassin after Vol'jin. He effectively turns Echo Isles into an internment camp. We can see he's paranoid. We can see under the tough exterior, he's scared. He's a tyrant who knows that what he has done has made people angry and he's trying to do everything he can to ensure they can't succeed in whatever they're cooking up.
I think it's cause he's got a really big body and a tiny little head.
My guess is he's sexually frustrated. He knows Thrall is settling down with Aggra, and with him still acting badboy without any high success rate on attracting any of his fellow female orcs he needs to let all his frustration out on everyone else.
To be continued in World of Warcraft: A Love Story, by Richard Knaak.
I think it's less about him getting simply more aggressive and simply that as time goes on he has the means and power to do what he wishes unlike before.
MoP is a special instance, where there is no real bad guy - the war itself is the villian here. Garrosh is merely an aspect of the war, killing him is a symbol. We killed the Warmonger, the Warchief, we killed the War. So, what next?
We all know war won't stop. Technical thing, this game needs PvP. In Vanilla and BC it was simple - 2 sides of the conflict, constantly scratching their past wounds, being unable ot approach diplomacy, but not getting much forther than clashing a few times a day because of lumber. Simple enough. WotLK changed this state, and created an actual backstory of the conflict and why it increased in scale. This time war is more of an official thing, and we see how and why both factions hate each other. In Cata the it's even worse, with a simple-minded, traditionalistic orc being the Warchief, and the High King not helping much. During Cataclysm we had the war at its finest, without a real "bad" or "good" side, but showing all the aspects of war and conflict, and consequences of it.
MoP changed it all. There is no clash of two enemies, who have reasons and make mistakes. Now it's simple "cowboys versus indians" game, where Garrosh is the bad guy, and Varian (for some insane reason) the good and patient leader. Now there are no descriptions or motives provided for the clashes - war is the evil itself, regardless of everything. Remember the Jade Forest cutscene? This is MoP in a nutshell. "Don't fight, and I mean don't, or terrible, shadowy things will come out and do mean things". I would expect that to be a part of a childrens book, not Warcraft lore. Lore that provides so intense and epic story of war and diplomacy as in WC3.
So now, when we stated that the War itself it the worst, meanest thing ever, what will happen after killing Garrosh, since the War needs to go on? After so many casualities, broken families and white haired Jainas? The logical thing is a short time of peace, since both factions bled too much. But it can't be done, Battlegrounds won't be closed in next expansion. Permanent peace? Same as above. The War goes on, and during MoP we accomplished pretty much nothing.
Thats pretty much the reason why current Blizzards writing has problems.
Just edited to say I give thumbs up for this. Tides of War is the worst reading experiance I've ever had.I think she was spending more time writing that excuse than her book.