Shields count as healing for that one, which is fair since as long as the shields break and the heals don't overheal you're basically looking at the same effect. Stackable additive health that doesn't suffer from diminishing returns like stacking mitigations on top of each other does. So most of that healing is coming from TBN. For the record GNB brutal shell would show up on that graph.

As for Requiscat, if we are looking at the healing capability overall going full clemency would be 5000. Considering were looking at 95th percentile of dungeon healing there's likely clemencies in there and yet DRK is higher than PLD. Of course it's not a direct translation of how it works as DRK would die without a healer and a PLD might live. Just trying to point out that 95th percentile there's probably some clemency in there (and to be fair might also be some Soul eater in packs in there). Yet just through the power of TBN and AD DRK is very much at the same weight class as PLD and GNB when it comes to dungeon healing/shielding in overall throughput.

Here's another graph