It’s not DR the problem, it’s the RNG tied to it. It’s the same issue I have with APs, with Sleep, with excessive damage fluctuation (all monsters which ignore defences).
If each Death Revenge monster had a condition to its DR that helped us predict who’ll get killed, or at least narrow down the possible doomed ones (e.g. the monster with the highest seconds, with the highest kills, of the opposite element etc), then it’d be a much more healthy and bearable strategy, at least in my book.
The same goes for Sleep, but I know both will never happen because they imply a MASSIVE rework. Still, I think that, generally speaking, more conditions should be implemented in order to progressively replace RNG, even if not completely by any means.