Alright, Nitro just investigated the DmndBR & SkullBR, and they do not do what BSiron thinks they do. Instead, they simply modify the enemy's Wisdom modifier, when they use Death on you.
See, the target's wisdom gives a base hit rate:
Target is enemy: 48/64, 46/64, 44/64, 40/64, 32/64, 24/64, 16/64, 0
Target is player: 40/64, 38/64, 36/64, 32/64, 24/64, 16/64, 8/64, 0
The caster's wisdom gives a modifier:
+0, +10%, +20%, +30%, +35%, +40%, +45%, +50%
(and the highest wisdom will just always work if the enemy uses Death)
(as in, the equivalent to a player's 205-255 range)
The SkullBR and DmndBR multiply this modifier by 1.5x and 0.5x respectively, but do nothing to the base hit rate of Death.
So, against Deathevan, for example, the DmndBR reduces the chance of Death working by about 15.5%, while SkullBR increases it by that same amount.
So, if Katt had 46 Wisdom, her base chance of getting hit by Death is 36/64. With Deathevan's Wisdom (45% multiplier) increases that to 52/64. Hence, DmndBR reduces that to... 44/64. SkullBR would make it guaranteed to land.
TL;DR, DmndBR is almost worthless, and the SkullBR is actively detrimental.
In simplicity is perfection