Originally Posted by
Swalload
The whole dying thing is only cool if we can't use the character at all after that.
But more realistically, I wouldn't be surprised if Sargeras was mythic only. And seeing how blizzard is pushing everyone into mythic with ToS normal and heroic being the easiest raid of all time, it would make sense to make a more "mythic only but still accessible to many" Sargeras fight.
I think it would be worthy of such a character to only exist in mythic, so we never truly see/fight a weak version of him.