Yeh, the 'middle ground' for all of the tanks (except PLD) was SHB.
PLD in SHB: Literally zero selfhealing in their rotation
PLD in DT: 1000p per 22s via Holy Sheltron, 1600p per minute from Confiteor combo, 800-1200p per minute from Holy Spirit/Holy Circle
WAR in SHB: X healing from Nascent Flash (X being equal to damage dealt, so weaker hits like Overpower = weaker healing. Also, on an ally the healing was reduced by 50%), 20% HP restored per 2min via Thrill of Battle, 1200p per 60s from Equilibrium
WAR in DT: 1200p (that is always 1200 and does not scale) per 25s from Bloodwhetting, 2200p per 60s from Equilibrium, 20% HP restored per 2min via Thrill, 1500p restored per 2min via Damnation
GNB in SHB: 1200p per 60s from Aurora
GNB in DT: 1800p per 60s from Aurora (now 2 charges too), 900p per 25s from Heart of Corundum, 20% HP restored per 2min via Great Nebula
Doing the maths, these three tanks (DRK's a little less egregious IMO due to it relying more on 'barriers' than 'direct HP restoration') have had their 'free healing via OGCDs that don't cost them any damage to use' increased by over 2000p per minute. PLD is expectially crazy, given it started with zero 'free' healing, so it went from 0 to about 5500p overnight
This also isn't including Barrier effects like Guardian and Brutal Shell, or the basic 123 combo healing like Storm's Path. Or the raidwide mitigations like Shake It Off (800p total) or Divine Veil (300p)
So, going back to SHB levels of self-sustain would be a big step. Wouldn't solve the issues overnight, but it's a start. Course, we won't be going back, because the Tanks would feel like they're not the main character anymore