i have both mnk and drg 50 (yep) and from my viewpoint MNK is harder to play, not because the cycles is complex, no because do it all the time is nearly impossible.
fight like ifrit that make you unable to attack even for 10 second screw the mnk all the way, you will loose your buff and will restart square one of your dps... meaning as the lowest one.

DRG come after, you need to take care of your position, make sure no magical attack hit you (or you will suffer if not die) you have a very long cycle with a lot of possibility off gcd. is not hard, but that depend of your tank, of your capacity to be where you need to be at the right time.

i will not talk of the other too much since i have'nt tested them too much at high level... but i doubt they can be more complex than Monk or Dragoon. anyone saying the inverse have clearly only read the forum and never try to play it.