Don't get me wrong - I am not Thrall hater - far from that. However, I think that battle against Deathwing was a pinnacle of his life - he was on top by the end of Cataclysm, and alas, any other deeds would only reduce his epicness. It is in good tragic traditions - a great hero defeats a monster but gets killed by a traitor. His burial would be really EPIC (think of Dumbledore's burial), a bright and tragic point at the end of this life. Trial on Garrosh would be more epic, too.
But the turn Blizz made.... Too much epicness truns a tradegy into a vulgar fairy tale - beacuse you know - WHATEVER happens, the Hero will always survive, and NOBODY dies, while he's a "good guy". Look, attack of Deathwing, the most powerful creature ever to step at Azeroth - NOBODY died among positive characters. Siege of Orgrimmar? NOBODY DIED (except for cannon fodder such as us).
And, one more thing here...Did Thrall receive god complex after defeating DW? He got pwned in one-shot, simply cleaved in the face by Garrosh in a fair battle, and laid on the floor while WE fought the "Warchief". And when WE've done the job, he stood up and came along with such a serious face as if it was him alone who defeated the tyrant, looking like a serious judge, like he wasn't lying face down on the floor a minute ago. And this is the second expansion ending cinematic where he plays role. What's next? "You disappoint me, Azshara?" "You disappoint me, Sargeras"? He has an addiction to wait until the raid defeats boss and then triumphantly come and deliver final blow?
Really, my opinion that Blizzard missed an epic ending and got Mary Sue instead...Unless they already have epic pland for him to be killed, as someone here recently guessed, by Jaina....
P.S. - I'm really curious to discuss another thing - during the last phase Garrosh mutated into a giant, hulking tentacled monstrosity, with eyes and blight all over him (so similar to Cho'Gall imo), and in cinematic he's clean once again. How did Y'Sharaj's corruption just disappeared without a trace so easily, and he shrinked back to normal orc? Didn't know that corruption was reversible... Did anyone else questioned that too?