The gap close

[CKNovel]

I was only pressing them because they were doing DMG

You have the answer to your question.

They were used a DMG abilities rather than mobility when they were first designed as mobility.
PLD and WAR gets to keep their damages because they already have little to weave os oGCDs. DRK, GNB and Dragoon have much more oGCDs.

In High-end content it was difficult to complete a burst while weaving mitigation (and sometimes doing a double tank swap) compared to GNB&DRK.