Some ideas I've had:

1. Shadow Wall: increase damage reduction to 40% from 30%, or reduce cooldown to 120 sec. from 180 sec.
2. Turn Dark Passenger into a defensive cooldown: 90 sec. cooldown. Reduce all damage taken by 20% for 10 sec. Upon expiration, release a wave of darkness around you that blinds enemies for 10 sec. and deals 200 potency damage. Dark Arts: Increase duration by 5 sec (both damage reduction and blind).
3. Consolidate Unleash and Abyssal Drain: Increase Unleash potency to 120. Dark Arts: Absorb portion of damage dealt as HP.
4. Bring back Scourge as a combo finisher: Deal 100 potency damage. Combo Action: Syphon Strike. Combo effect: apply Scourge on the target: 40 potency, 18 sec. duration.