for what it's worth, i'm of the opinion that we get the last laugh for the vast majority of the game. i mean, ultimately... killing that red/purple named boss? what, that's like, under a minute in most quests. in raids, it's a bit worse, but still.
dealing with all the trash between the start of the quest and the end? well, guess what... that's what i do as a caster. just you go ahead and find the dps who can make the run up to the end boss as smooth as a good CC-spec caster. which means that when you finally do reach that end boss, hopefully your healers have plenty of mana, the melees haven't burned any major resources, and your caster is the one they have to thank for it. so what if you're not uber leet dps on the main boss? you could probably have solo'd the entire quest right up until that fight if you had to, the only reason they even came along was to make it faster and to deal with the boss. in some quests, it's entirely possible the only reason they even *saw* the end boss is because you got them there. your time in the limelight has probably been way longer than theirs anyways.