I think it’d be really nice for Death Seal to have a toggle/aura node. Life/Endurance-based Low Life Acolyte using Death Seal: Deadlock feels really fun to me, but having to refresh the skill basically on cooldown and having HP in the spicy zone for a second after Death Seal’s duration ends feels pretty bad, imo.
There are definitely a lot of node interactions that would need to be considered, but looking at the tree it doesn’t seem to me like a lot of them would be too difficult to hammer down how they ought to work, and nothing leaps out at me as obviously or massively overpowered, except maybe The Quick and the Dead if it weren’t given a cap on duration, and Necrosis/Leper’s Skin for abusing with one-time ward generation.
Node location, maybe it could be behind Deadlock or Grim Scale? (Though with the latter, I’d personally like to see Life Tap moved somewhere else…) And saddling it with a bit of mana drain or some comparable cost would make sense.
As an aside, I also think it’d be neat to have some Intelligence scaling available somewhere on its tree. Losing out on the Ward Retention that Int inherently provides while Death Seal is up doesn’t feel fantastic, especially when Liches have so many passives to get buckets of Int (there’s 46 total Int available on the Lich tree!) and multiple other abilities have additional Int scaling - my current Lich is running Soul Feast: Hellmind, Spirit Plague: Plague of Eyes, and Reaper Form: Soul Shroud & Vile Shroud, for instance.