Are you kidding? MNK's need for positionals are definitely not as punishing as you make them out to be. In addition to this, there are very very few fights where this is a thing. The only one that comes to mind is T9 during the final phase - and that is purely due to a strategic choice. Even then, there are only certain times where the MNK does have to stack with the party during this phase (and that is Fire in, and potentially the Thunder that is paired with a Lunar). Every other time DPS can be wherever they want.
Almost every mob that isn't a trash mob will regularly spin around to do special attacks on non-tank targets and cause positionals to fail. The whole "very very few fights" thing is total baloney and you know it.

MNK to play "fairly well" is much much much more braindead and easy then NIN is.
If that were true, it would show in my numbers, considering NIN is a job that's far newer and I have considerably less experience playing it. It does not.