Block not scaling anymore is a non-issue.

In fact, it solves the issues we had back in SB. Block scaling wasn't just insane, but outright overpowered. Being able to mitigate 30% - on the same level as Vengeance and Shadowwall - on a 5s recast, usable every 22-23s on average, made Sheltron even stronger than Vengeance/Shadowwall in most cases.

Also, the ability to block magic in SB also made DRK obsolete. While in HW, DRK was a anti-magic/parry tank, PLD was focused on physical defense, and had weak magic mitigation. In SB DRK lost Dark Dance/Anticipation as its unique CD, but Dark Mind was left untouched. At the same time, block could mitigate magic attacks. In addition, PLD pDPS made a rocket jump, leaving DRK behind in terms of mitigation and DPS on average player skill. (They "fixed" some of this issues later on with DM having 30% base mitigation.) Now mix in Cover's trait 20% bonus mitigation, and party utility (PoA + DV) and PLD had a secured spot in most parties. WAR being the "DPS tank" during SB gave them a good spot, too. DRK wasn't needed - and too hard to play, unforgiving, or just not rewarding.

In ShB, block scaling is gone for good. And that's fine! Content is designed around multiple jobs. If just 1 single job would benefit from scaling, it would either make them either superior or even mandatory over the course of an expansion. Current and upcoming content is designed with current mitigation toolkit in mind, so the toolkit should not change.

PLD still has one additional party mitigation ability over the other tanks! (PoA+DV vs SiO vs HoL vs DMis)
Also, having 1 less pCD doesn't hurt PLD due to its passive blocks. (And as a DRK, I would always take passive mitigation over 5.0 Dark Mind)