I used to be 100% convinced that questing is the only way to level, but then I rerolled on Mag which is PvP and I'm rethinking that approach. After a long Sunday spent in the Tarren Mills area I spent so much time getting ganked and having to corpse-run, or wait for town NPCs to respwan, that I'm starting to think that it might be more efficient to just grind in instances, where noone can bother you.