from level 1 to 30 -> druid is a good and fast PLer.
from level 30 to 70 -> SK well stuffed is the BEST class for PL
i used to get PL by a SK 70 PoTime stuffed from level 30 to 46 by this way :
the SK pull a train, put mobs to 2% hps, FD then cast aggro spell to keep mob on him, then i give the last hit and get xp --> if u hardcore play u can do 10 level a day
from 46 to 49 (and more), i grouped with him and clearing some zone like The hole and CoM (while doing my epic) (phantom revenants are kewl damnt good xp -> 3% a hit :p) and we did it in 1 hour and half
from now i guess we'll head to PoJ or PoD or PoN :p gonna check out the fastest xp of those zone