this is very weird though, super poison should be a better proc because it is specific for 3/3 set, but compared to instant kill proc:

both can't deal (or supposed to be) damage to boss
both are rarer to proc than the other
instant kill deal 100% health, super poison 'only' deal 50% health to mobs
instant kill only need the weapon, super poison need the whole set

from the comparison, instant kill proc >>> super poison, but it takes more requirements to proc the super poison (must have the full set), which imo doesn't make sense.

it will half make sense if super poison can work on players, where instant kill shouldn't, so the next question is, is the super poison meant to work against player?