This will probably not gonna happen in FF14 but I have ideas about turning DRK into a stagger/recover tank (Brew/Blood DK hybrid).

Haven't really fleshed out the idea, but it basically involves TBN absorbing damage, turning a portion of the damage back into mp, and then diverting the damage absorbed into the DRK as stagger damage over the course of 10 seconds. Bloodspiller would then be used to reduce or remove the stagger damage, adding the stagger damage removed to the base Bloodspiller damage.

If TBN breaks however, it stores that damage in you as a debuff that makes your TBNs squishier. Popping Delirium would turn the debuff stacks into stagger damage that only starts ticking after 10 seconds, giving your Bloodspiller the meatiest biggest hit.

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I just don't really the fact that Bloodspiller is spammable in current DRK. It kinda lowers the oomph of the skill compared to old Dark Arts Bloodspiller