Personally, instead of changing abilities around I think DRK needs to have its core functions changed and reworked. For example, I would like to see it as an evasion tank that built up stacks of evasion over time, perhaps call it Embrace the Dark. So, stacks of ED would increase and have a timer based on usage of a cool down that is aligned to that mechanic and/or being hit. This raises your chance to evade. It would be unique over the PLD and WAR. Instead of mitigating you're outright avoiding the damage.