I don't mind that storytelling device per se. It works pretty well in single player RPGs, although it can get stretched pretty thin there as well (hi Mass Effect, I'm looking at you). In a large scale cooperative game, being told that I'm the only one who can kill Dragon X is not very convincing when I have to stand in line and wait for three other people to kill it first. And then when it's my turn, I'm killing Dragon X while standing on the corpse of... Dragon X. And also Dragon X.

Yeah, that just doesn't work.