The way he died wasn't too bad, but the way it was handled...
Hypothermia.
Deathwing turned into stardust. He's up there now watching us all!
If Blizzard wants Deathwing to return they will find a way to bring him back, nothing more to it. Just look at Deathwing's backstory, he was thought to be killed multiple times and he always came back. Now, I have to agree that surviving this one would be truly something, but I repeat, if Blizzard wants it then it will happen.
Same thing with Teron Gorefiend, he came back from death multiple times as well and his death quote in Black Temple seems to suggest we'll eventually see him again.
Or what about Illidan coming back from the death? Cho'gall coming back? Many characters return if Blizzard wants it to happen.
Yeah, that's right. None of us should still exist if Nozdormu hadn't created an alternate timeline by snatching the Dragon Soul from the past and defeating Deathwing with it. The End Time was the correct timeline and should've happened.
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Ehm, if you want Azeroth to look like End Time, sure!
Its actually soloable atm if you are a geared tanking class. Its easily 2 mannable- i run with a shadow priest and easily clear the entire instance on my druid tank (He only goes healer for Ultrax, as that fight is currently the hardest fight in there to do with few people)
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For those saying that the DS thing can be erased with time magic, it cant- Nozdormu expended every bit of his flights time-magic in order to make it to where the Madness fight thing happened in every single timeline ever. It's why the bronze dragonflight are unable to do more then take sneak-peeks at time, and then only with outside temporal magics, like the epoch stones.