Or possibly something that gives them a better negative energy strip than what they have now.
Yeah honestly I would love that, I was mostly thinking about this design for thematic reasons, just because the name of the item is "Death's Deferral", but then it had like, accuracy and deadly. The only thing about the item that "defers death" is Death Ward, Mass, which ok yeah that makes sense, but I still think it would be a better thematic match if Death's Deferral is the premier "I'm a necromancer trying to cheat death" item.
Negative damage is (and always has been) in such a bad place because the only strip (that I know of) is T4 Pale Master, and that only affects undead. Constructs (of which there are a great many in this game's content) remain a consistent problem. The other issue with Pale Master's strip is that (as normal) you have to hit the target with negative energy first, and unlike most other strips where the biggest value comes from creatures that are Immune to the damage, undead all
heal from negative energy, so if it's not the first thing you hit the target with (or your party members) then you're going to heal the undead first, so that you can start doing damage later.
Personally I think that Pale Master's T4 enhancement should be reworked so that your spells never heal enemy undead, and you get a full on negative strip, not just for undead.
But if they made a raid item that did that first, I would be all about it! After all, not all negative builds go into Pale Master so it would still have value either way.