ZOS thought it would be more important to fix shadowy Disguise, that was not granting 100% Crit Chance to Spells. That was ofc. more important than Dark Cloak, cause we are talking about Magicka Builds, not doing TOP DMG.
All of the shadow cloak variants are still in a sorry state. They all get ignored at random by mobs while in effect and they all drop when the NB's dots tick on an enemy, dark cloak just happens to have one more bug in that it fails to remove negative effects.