Aaaand there you have it folks, the reason why PLD can't get buffed - because DRK has issues.
Bud, this isn't a "DRK is op and shouldn't get buffed" thread. DRK can have sustain problem and PLD a damage problem simultaneously. A lot of people who think PLD should get buffed also agree that DRK should get some sustain and QoL (or, you know, actual cohesive job design). Both can be true at the same time. In fact buffing PLD would make it even more apparent that DRK's state is not okay and thus a bit more likely it'd get changes as well.