Yep, only powerlevel if the person has experience beforehand from another job. Powerleveling new players leads to Warriors in Valkurm not knowing what Provoke is, or Black Mages with just Stone still.
Also, if your helping someone PL, and they die due to some circumstance, don't bother looking for a raise. The XP you lose can be quickly made up, best bet is to go back to homepoint and walk back to your previous spot. Hell, even if you get a raise quickly, you still need to deal with 8 minutes of weakness (I think its 8).
I was thinking also, if you happen to have Bard with a few levels, maybe you can quickly keep PTing and singing 2 songs, then disbanding with the person and having those songs effects remain for a little bit. I've never tried it, but maybe it works, give it a shot if you got Bard, I know I'll be trying it with my friend once he unlocks his advance job.