Ok so... underbog is nice so far. Can do everything up to the second boss in 1 pull. taking about 1-1.5 hours per level on the toons. Not sure how it'll do up to 70 though.

Tried some others:
- Mana tombs: crap. 1 small pull before boss, next big pull has aoe healing priests and all the mobs stay at 100% hp forever.

- Sethekk Halls: worthless. tank gets charmed every 5 seconds and group wipes

- Crypts: not enough mobs, not enough elites

What else?
Just do underbog to 58 and then Uk to 71? A lot of people are paying 50g a run for underbog though