Here is a thought
Does a wardens sword negate deathcurses? maybe that's why they use them as well!
No, or at least not by default, though it's counterspelling function might help a bit. We know it doesn't negate them because in Dead Beat there's a discussion over the cooling corpse of a wizard slain with a Warden's Sword about how lucky they are he didn't do a Death Curse.
Though I wouldn't be surprised if, at formal executions (where Senior Council Members are sometimes in attendance, mind you), there aren't a variety of protections up against that sort of thing. If you assume that they mostly kill as part of the formal process, it looks alot less bad for them death-curse wise.
