I main a Dark Knight, so here are some ideas to make it better.

1. REDUCE the cost of Dark Arts.
2. Abyssal Drain should automatically give you HP without the use of Dark Arts.
3. Dark Mind should be a group wide mitigation when you use Dark Arts.
4. Reduce the cool down for Soul Seeker.
5. Delirium potency should be higher or cool down should be shorter.
6. Carve and Spit should give HP or MP based on damage dealt under the use of Dark Arts.
7. Bloodspiller should cost less blood, or cost abit of TP.
8. Unleash should have a higher potency.
9. The Blackest Night should turn into a group wide sphere that can shield from damage and give blood based on how many players are in the circle upon using Dark Arts.
10. Living Dead should NOT kill me if I’m not healed fully in a certain time after.
11. Blood Price MP return isn’t to great, so maybe increase the duration or increase how much MP I get with every hit?

That’s about it!