I will go a little farther and not only put what I think is / should be culled / added but what I'd like to see modified.
Actions Culled
1. Blood Price
2. Blood Weapon
These are removed as their own individual actions, instead becoming fundamental parts of Grit and Dark Side. Their function in the current kit will not change overmuch, but they are still being 'removed'.
Edit - On further consideration
Black Blade and Dark Mind existing together steps on each other toes while also expanding the Dark Knight's kit against magic damage to a nigh broken degree. Of the two, Black Blade simply offers more.
3. Dark Mind
Actions modified
1. Dark Side
Rather than be Gritless, Dark Side is the de-facto Not-Tanking stance. The two are exclusive from each other. The Dark Knight builds blood and MP by dealing damage with weaponskills.
The Dark Knight's attack speed is increased, ranging from 5% to 15%, with the highest bonus attainable when over 75% maximum HP.
Upon activating Dark Side, the Dark Knight delivers a cleaving strike to all enemies in front of them.
2. Grit
Grit is the de facto Tank stance. Grit's prior bonuses do not change, still granting increased damage reduction and increased threat generation. Grit will no longer inherently reduce damage dealt.
Grit Dark Knights build blood and MP primarily by taking damage.
While in Grit, the Dark Knight gains increased parry chance and increased parry strength.
Upon activating Grit, the Dark Knight drains health from all enemies around them.
3. Unleash
Instead of removing certain abilities, we trait them, removing the need for level swapping, while adding a more tangible sense of progression. (While Abyssal Drain is superior, Unleash serves the purpose until it's gotten.)
With this in mind.
Upgrade Path
Unleash (Level 6) -> Unmend (Level 15 trait) -> Abyssal Drain (Level 54 (or wherever it was) Trait))
Unleash is modified thus-
Dark Arts: Gain the damage dealt as health.
Unmend: Unleash, when an enemy is targeted, additionally sends out a ranged bolt of energy at the target in addition to current effects.
Abyssal Drain: Unleash, in addition to current effects, now also deals the ranged damage in an AoE around it.
Animation change
Unleash: Unchanged
Unmend: Abyssal Drain's motion, Unmend's spell effect
Abyssaldrain: Unmend's motion, Drain's spell effect.
I didn't count this as removal as it just makes more sense from the angle of ability progression. In this same manner, Warrior's Brutal Swing should have more gracefully transitioned into Upheaval.
4. Sole Survivor
Gains a trait in the 61-70 range. Soul Drain. Drains 30% of the Dark Knight's maximum health from the target. May be activated early to gain the health immediately, but do damage and drain MP proportional to the time left.
5. Delirium
Recast: 120
Effect: You gain the MP and Blood generation of either Dark Side or Grit, whichever is not active, for 20 seconds.
Actions added
1. Black Blade
Blackblade - Ability
Recast: 45 seconds
Effect: Raise your blade for 3 seconds, parrying the next attack flung against you. Blackblade enables parry against Magic damage.
Dark Side: Blackblade deals a retaliatory strike for 220 potency and increases the attack speed bonus of Dark Side by 100% for 10 seconds.
Grit: Blackblade deals 120 magic potency to enemies around you and increases parry rate to 100% for the next 2 attacks against you.
Vita In Morte
Vita In Morte
Spell
Cost: 50 Blood
Effect: Grant yourself 100% Life Drain and 25% increased MP returns for 20 seconds.
Shadowblade
Shadowblade
Ability
Recast: 45
Effect: Mimics your last used weaponskill at the target, dealing 100 potency and applying any additional effects that were present.
Dark Side: Shadowblade counts as a weapon skill and deals the damage over two separate strikes.
Grit: Shadowblade's cooldown is reduced each time you parry.
Reprisal
Reprisal
Ability
Channeled - 15 seconds
60s Recast
Effect: Reflect attacks taken for 30 potency while channeling. Moving or using another action to resolve Reprisal causes it to deal 100 potency to enemies around you. Each time you take damage, Reprisal's final potency increases by 10.
Dark Arts: Reflected attacks have 100% life drain. Final potency increases by 20 each time you take damage.
Dark Side: Reprisal counts as a weapon skill.
Grit: Gain the damage dealt as healing. Overhealing converts into a shield, up to 20% of maximum health.
Scourge
Scourge
Weaponskill
Recast: 1.5 seconds
Effect: Strikes twice for 75 potency. Marks the target for execution for 30 seconds. Scourge's potency increases by 15 against the target every 3 seconds. Using Scourge again resets the bonus.
Scourge must follow Bloodspiller, Quietus or a Combo Finisher.
Dark Arts: Scourge strikes one additional time.
Dark Side: Scourge's duration increases by 15 seconds.
Grit: Scourge applies at half damage for all enemies around the primary target.
Button Economy - 5 removed, 5 added.