Yes, power leveling does indeed still work when done right.

Partying with a healer for FATEs is also good, you can whip through them quicker. Controversial, but Levequests. They stack up quick enough so that if you do Levequests at your level, like 10 a time you will get a tonne of experience and possibly level up. You'll also get gil, ventures and other equipment that would match your level.

Level 40-50 is the quickest, for me it is always 30-40 that sucked!