I didn't assume anything, I used math involving averages for comparison because both Featherfoot and Keen Flurry are based on RNG.
Yes there are attacks that you can parry but not dodge, however on every one of those fights I can think of, Mantra or Feint is the better choice for the 5th cross class skill.
I also gave a SPECIFIC example that was actually useful to the OP (rook in phase5 of Turn4).
So...