If any, I personally see Field Operation as "Casual content but with potential to be midcore'ish". They're relatively easy to 'clear' down to the last quest, but that's where the casual line starts to blurr into: you're certainly not required to gear up your elemental+2, getting physeos weapon stats roll, optimizing LAs setups, farming fragments to be sold to make bazillion gil, grinding the 3 rays, etc.