No one, especially not me, is telling GL sustaining is fine and fair.

The point is just : things cannot be compaired if they aren't comparable. Armor crush can only be compared to whatever extend the duration of GL : coeurl form strikes. Telling that nin doesn't have to refresh it 3 times as Armor crush is a decision that can be delayed and coeurl form attacks are an automatic cycle. Give +15s to huton on aeolian edge and shadow fang and no one will ever touch AC anymore, because it's a decision, and Coeurl form attacks aren't.

The punishing aspect is none to be compared, because the whole design of GL was turned, as the heavy positionnal, to the relative difficulty to properly play MNK and be top DPS. However, this design is flawed now, and monk is just one amongst other DPS and nothing is a justification to it's exigency.