I have all 60's but a zerk/mystic. (Mystic @ 55, zerk at 27)
Easiest classes to level: Sorc/Zerker
Sorc/slayers/zerks are preferred DPS atm for end game (will change when people stop being brats..) - Mainly best for leveling as they have aoes/360 attks.
Zerks are really awesome for their dmg/block.
Archer is alright, found the leveling OK, but not as fast.
Priest/Mystic aren't bad, but definitely not as fast as the DPS. (Mystic is a lot slower than priest, but with adjustments on glyphs and crystals, there's np.)
With the mob boosts later levels get extremely annoying (HP gets 100x bigger = more annoying)
Lancer/warrior, on par for me. I don't personally like the warrior (fast attks but small #'s).
I loved leveling lancer but again, dmg def not near the dps.