For me in order from best to worst

B) Camping (like FFXI)
D) Moving around, killing hardest mobs (30-40 secs per mob light party)
F) Dungeons
A) Quests
E) Guildleves
C) Moving around killing mobs as flys (10 secs per mob solo/duo)

Camping and Roaming partys are still my prefered way to level, followed by dungeons in mmos outside of FFXI/FFXIV.
Quest based leveling is ok, but the solo aspect of it I feel takes away from the mmo, Guildleves.... I am sick of them and zerging crap... that should never be a tactic for leveling or any major focus in a mmo.