A death penalty is a short sighted change to scoring. I say that because ultimately everything comes down to time. Once there are no death runs, and there will be, then time will be the only factor.
Furthermore, I don't understand why we would want deaths to count toward the score when it is mostly 'randomness' causing deaths and when deaths already do penalize a runs time. Is making deaths count twice against a score really the goal? Isn't it more interesting for groups to be able to "save" a run by making up time that was lost due to a few run by having later outstanding play?
Based on your next comment about how meaningless vDSA is from a difficulty perspective, I agree that difficulty in these places could be raised, but also think that the nature of the game and speed runs will not allow for that difficulty to be meaningful for very long. That is the whole nature of progression and speed runs. Through practice and become stronger we trivialize what was once difficult.
Maybe find a new way to challenge yourself. While gimping yourself doesn't feel good in and off itself, it can still make for fun gameplay. 5 man sanctum is pretty interesting.