Dark Knight
Changing Dark Knight's The Blackest Night to either to not granting Dark Arts, reduce Edge of Darkness potency from 1000 to 800 or reduce the "Reduces target's HP recovered by healing actions by 20%" to reducing recovery by 10%. One of these changes would help bring Dark Knight in line with other tanks.

Changing Edge of Shadow "Reduces target's HP recovered by healing actions by 20%" effect to either not stack with, or alternatively overwrites, Scholar's Biolysis debuff, and vice versa. Or as mentioned in the Scholar feedback, create an entirely new effect altogether for Biolysis so the stacking isn't an issue.