It depends.
DH for my guess is the worst because its too squishy.
Crusaders dmg is very rough in terms of gearing , very similar to barb. HOWEVER - if you could build thorn dmg crusader its OP.
Wizards are nice.
Barbs are nice - they need some gear tho , however after u gear them they are beasts. Right now my barb is missing a lot of good items , and I crit for 40mil rough. I do t5 ghom in 10-13 sec.
Monks are decent too.
WD is bad idea I guess , his playstyle is too situational. Unless u get full zuni & build pet dmg its hard to bot with WD.