It's a bit more naunced than that. Before 6.X PLD had 0 selfhealing in any normal situation, which wasn't nearly compensated by the slightly higher mitigation, and didn't feel very good imo. This was the state of PLD sustain in 5.X
https://www.fflogs.com/zone/statisti...unt&metric=hps, and for dungeons
https://www.fflogs.com/zone/statisti...ps&class=Tanks Like always it's a balancing act. PLD sustain now to strong, but it did actually warrant some buffs after 5.X.
Removing healing from the Requiescat combo and Holy Sheltron would feel a bit jarring when you level up. At level 84 you finally get some much needed self healing. But a few levels later, that would be significantly reduced against when you switch from Requiescat > Holy Circle/Spirit spam (with selfheals), to the level 90 Requiescat combo (without selfheals). For PLD selfhealing nerfs I'd remove healing from all attacks, and increase the healing from Holy Sheltron a bit.