Hmm, I always go to 40 in SM... how badly did the XP drop off? I didn't think it was too bad.

I will tell you ST is rather bad because trolls run away, and also turn you into a frog. So you think Dragonkin ! but they still nuke you pretty hard and put you to sleep. You can try it though.

I would lean towards BRD, or dig up all the graves in ZF.

edit: Yeah, dug up my notes on ZF... digging up all the graves by the Witch Doctor boss was a bit over 2 bubbles @ L44, pre-RAF bonus. It is a little slow getting there because you have to be careful not to pull too many totem guys, but there aren't any or more than 1-2 shadow hunters (hex) on the way. But with RAF it should be most of a level I'd think per run. I got it down to ~1 hour per level in the mid-40s in ZF so... x3 = 20 minutes or so per level. Not too bad.