Not true. WAR only RECENTLY has been able to heal at this level to the point they can solo a dungeon by themselves and bring nobody else in if you know how to optimize your cooldowns. ARR and HW they didn't have this level of healing since they heavily relied on role skills to even do so; it still didn't outweigh the damage intake they were receiving from normal fights compared to Bloodwhetting right now.
Not even in Stormblood or Shadowbringers were they capable of sustaining themselves to this point. They always were reliant on healers and the party to actually heal themselves. If you look back to as far back as Heavensward, DRK had that same thing going for it when Abyssal Drain was an actual GCD and you took a giant mob pack; you were just limited by your MP at that. Then they stripped it of that self-sustain when they redid everything in Shadowbringers and set the slate clean across all tanks; and they felt rather nice to be close to each other in terms of efficiency(even when people weren't liking DRK's new design). Right now, WAR leverages all the burden off of healers and instead is able to unga bunga their way to full HP via their GCDs that grant 100% of damage done as HP. That's a lot with current HP values.
If anything, no tank should be able to solo content or even group with 7 other WARs to beat half a Savage Tier. What are healers anymore?