Lithose's idea is interesting, yes. I sometimes find myself thinking about a less radical idea that could perhaps lessen drop frustration: why not give guilds a choice to *exclude* one item from the loot table for the kill?
It could work more or less like this: after a boss is killed, and before loot was displayed, the raid leader would see a window with the boss' loot table and s/he would choose one item that would surely *not* drop - and then everything else would be randomized normally. Of course, I don't know how much work that would imply on the programming side (since loot seems to be generated when players enter an instance, and this suggestion would obviously change that), this shouldn't be allowed for tier tokens, and this might put too much power in the raid leader's hands - but, hey, if you can't trust your raid leader, s/he shouldn't be raid leader in the first place, right?
This would keep loot random and "exciting" enough, and would likely make it more rewarding. Just imagine being able to never see
[Antonidas's Aegis of Rapt Concentration] again...