My team of four is level 28/29 atm.

I've been powerleveling them with my 70 'lock in SM Cath for 6 levels. Cath sets up well for SoC, so I went there instead of library/gy.

Its about 3 - 4 clears for a level. I can clear it comfortably in 20 mins. (I'm sure it can be done faster.)

I can't imagine generating a sustained 10k exp per 20 minute (30k per hour) rate questing at this level. While it gets mind numbingly boring, it sure feels like there's nothing more efficient. (I'm not looting, btw.)

When I get bored, I do some PvP with my 'lock. Thinking I'll do this until SM Cath wears out (38'ish?). I may try ZF, but I'll admit I've not been there in ages and I'm not sure when my 'lock's PL'ing ability will stop working. (I can get owned doing SM if I somehow lose a SoC and get 5+ mobs on me.)