Experience rewards for Dungeon entries in the challenge log are the same up to level 60. Feeling Lucky (3 dungeons via the duty roulette) gives 15% of your current job's current level. Dungeon Master (5 dungeons) gives 10% of your job's level.

My 51 paladin (1,058,400 experience from 51>52) gets 158,760 experience from Feeling Lucky, and 105,840 experience from Dungeon Master.
My 34 lancer, if I were ever inclined to level it given the days of cross-class are over (217,900) gets 32,685 and 21,790.

Except at level 60 the equation breaks.
My level 60 white mage (4,470,000 experience tnl) gets 583,200 experience from Feeling Lucky, and 388,800 experience from Dungeon Master. That seems off.
My level 65 red mage (6,995,000) gets 583,200 experience, and 388,800 experience. Wait a minute.
I asked my friend, and their level 63 monk (5,809,000) gets 583,200 experience, and 388,800 experience.

Any of that seem off to you?