I don't find even gathering quests that bad. But I have to admit I like questing. When it is at least the second time in a zone, with QuestHelper and such, the routes can also be very optimized.

It also heavily depends on group composition. I am currently busy levelling two new groups through outland. One is fine for instances (Pala, Shaman, Rogue, Priest, Warlock) and the other is not at all (5 x Arcane Mage). When I get the dreadful "No more instance can be launched" message with the first one, I just switch to the mages for a little questing session.