Thought I would share my thoughts on how they could work for tanking. Long post incoming.
Dark Knight Job
1. Violent Slash--Deals damage with 150 potency. 15% chance to absorb 50% of damage dealt as Hp. On GCD. 70 TP
2. Blood Weapon--Doubles damage of next weaponskill and returns damage dealt as HP. 40 second cooldown.
4. Darkside--Deals damage with 100 potency. Increased enmity. Combo bonus from Violent Slash: 200 potency. Debuffs enemy for 5 seconds so that 40% of damage dealt in this time is returned as HP. On GCD. 60 TP
6. Drain--Casts a spell that returns damage done as HP. 120 potency. Increased Enmity. 2.5 second cast. On GCD. Costs MP.
8. Black Sky--Instill fear in surrounding enemies, forcing them to attack you. Increased Enmity. Deals damage over time with potency of 20 for 18 seconds. Damage dealt heals user by half. Instant cast. On GCD. Costs Mp.
10. Blood Pact--Sacrifice 10% of HP but decrease damage taken by 50% for next 6 seconds. 150 second cooldown.
12. Redeemer--Deals damage with 140 potency. Slows enemy by 20% for 20 seconds. If enemy is immune to slow, damage dealt by next Violent Slash increases by 20%. On GCD. 80 TP.
15. Shadow Energy --Deals ranged damage with 120 potency. Increased enmity. If enemy has a DoT, there is a 15% chance the Dark Knight will absorb half of its total potency as HP. On GCD. 130 TP.
18. Diabolical Eye--Increases parry strength by 25% and rate by 10%. Allows a 100% parry rate for next 5 seconds after activation. After 5 seconds of 100% parry rate, this parry rate will be unattainable for 180 seconds. Allows Dark Knight to parry magic. Decreases damage dealt by 10%. Increases enmity gained by all abilities. Stance with 10 second cooldown. Cannot be used with other stances. Changes effect of Threaten and Omen.
22. Dismember--Deals damage with 100 potency. Returns damage dealt as HP. Combo Bonus from Redeemer: Adds a DoT with potency of 30 for 15 seconds, while negating HP return from initial hit, instead returning the DoT as Hp. If a DoT crits, this ability costs 0 TP without a combo bonus. On GCD. 60 TP.
26. Threaten--stuns enemy. With Diabolical Eye, it becomes a pacify. With Arcane Circle, it lowers enemy damage dealt by 10%. With Dark Seal, it silences enemy. 20 second cooldown. Costs MP.
30. Vicious Cut--Deals damage with 100 potency. Increased Enmity. Combo Bonus from Darkside: 270 potency. Makes enemy deal 20% less damage with next 2 auto-attacks. On GCD. 60 TP.
30. Arcane Circle--Locks MP in place for 5 seconds after activation. After 5 second lock, MP cannot be locked in place again for 180 seconds. Increases MP regeneration rate by 100%. Damage taken reduces MP instead of HP until MP runs out. Increased Enmity. Cannot be interrupted when casting spells. Stance with 10 second cooldown. Cannot be used with other stances. Changes effect of Threaten and Omen.
34. Death--Instantly kill an enemy under 20% HP. If enemy is immune, deals damage with potency of 500. 40 second cooldown. 5 second cast time. Costs MP.
35. Dark Seal--decreases damage taken by 15%. Increases HP restored by self-healing attacks by 30%. Upon activation, HP is replenished by amount of current MP. This method of obtaining HP will become unattainable for 180 seconds after being used once. Reduces damage dealt by 10%. Increased enmity. Stance with 10 second cooldown. Cannot be used with other stances. Changes effect of Threaten and Omen.
38. Mind Breaker--Deals damage with 100 potency. Returns damage dealt as MP. Combo Bonus from Redeemer: Adds a DoT with a potency of 15 for 30 seconds. If a DoT crits, there is a 50% chance cooldown on Blood Weapon will be restored.
40. Doom--calls forth a demon to take an enemy's soul. Enemy's str, dex, mind, and int are reduced by 5% for one minute. After minute expires, enemy dies, or if immune to death, enemy takes damage with potency of 600. 2.5 second cast. 240 second cooldown. Costs MP.
42. Dark Spikes--Drain MP at 1% a second to maintain this ability. Reduce damage taken by 5%. Every time enemy attacks, deal dark damage with 10 potency. Each counterattack has a 15% chance to allow the use of any weaponskill without a combo bonus and for half TP.
45. Soul eater--Sacrifice 10% of HP to attack all enemies in a frontal cone. Deals damage with potency of 210. Increased Enmity. Can only be used when HP is above 75%. Increases Defense and Magic Defense by 2% for each enemy hit for 20 seconds. 30 second cooldown. When in Arcane Circle stance, this ability sacrifices 10% of MP and still requires HP to be above 75%.
46. Nether Void--Sacrifice 10% of HP. The next two attacks taken do not injure the body, and damage taken by them will be percentage based. Each one removes 3% of HP. After effect disappears, the Dark Knight becomes buffed and received a 20% more HP from healing magic for 20 seconds. 120 second.
50. Omen--After 20 seconds, reduce the damage the enemy deals for 30 seconds by 10%. With Diabolical Eye, the enemy takes 10% more damage for 10 seconds. With Arcane Circle, the enemy's accuracy and evasion are reduced by 20% for ten seconds. With Dark Seal, the enemy will now take 200% damage from critical attacks instead of 150% for 15 seconds. 2.5 second cast time. 100 second cooldown.
50. Last Resort--allow HP to reach zero without dying for 6 seconds. Sacrices the Hp of the target ally to 1% to restore all of his or her HP to you, on the fifth second. This makes the ally invulnerable to damage for 10 seconds. 300 second cooldown.
54. Charon--deals damage with potency of 180. Increased Enmity. Combo Bonus from Vicious Cut: 310 potency. If enemy dies 10 seconds after this ability is used, 10% of HP is restored and 20% of MP is restored. On GCD. 70 TP.
58. Confuse Ray--makes next enemy attack target its ally if one is available with next ability, dealing only up to 80% damage with the attack. Dark Knight will split the damage with the target by half. If it cannot attack any allies, it will attack a shadow. 80 second cooldown.
60. Dominion Over All--Deals damage with 180 potency to all nearby enemies and binds them. Reduces damage taken by 20% for 10 seconds. 2.5 second cast. 60 second cooldown. Costs MP.