So there's been a lot of discussion about Dark Knights and how they'd be implemented and various discussions of the kind, so I decided to weigh in.
My interpretation would have Dark Knight as the extension of its own new base class, the Reaver, a heavy armor tank wielding a two-handed sword. It's set up with 2 ST combos, one of which is the basic damage/enmity generator and the other which is a support/tanky combo that has to be built up and then maintained. I also decided to play around with an idea and have a 2 part AoE damage/enmity combo. The CDs, both tanky and damage, are built around sacrificing hp to gain the requisite benefit, which I thought to be pretty apt.
The Dark Knight adds a bit more. The tank stance reduces damage, as it's supposed to, though the increase mitigation it's supposed to provide is accomplished by increasing magic defense and drastically increasing parry chance/value (at ~10% default parry chance at ~20% default parry value, the increases should equate to roughly 20% damage reduction, though it would be spikier thanks to being RNG based). It also allows for easier acquisition of the "Darkness" buff, which is a single stat "resource" consumed by a lot of other Dark Knight abilities. It *isn't* contingent on having Dark Ward (the tank stance) active, so that you can still use Darkness consuming abilities while out of the tank stance, though it's much harder to get it (i.e. only gained by using the Darkness granting CD). Unlike Wrath, Darkness is only provided by the end ability in a combo, rather than each combo action. There are 3 Darkness consuming abilities: one AoE with a bit of healing, one ST, and one tanky shield. I tried to make them more useful than the WAR ones, mainly by reducing the opportunity costs to a reasonable level.
As I've done previous times, the abilities aren't listed at the level gained, nor are they presented in the order in which they would be gained. They're organized, roughly, in categories of relevance to each other.
Reaver Class Abilities
Darkness increases all enmity generated while it is active by 25%
1. Vicious Swing: Potency 150
2. Devastate: Potency 100, Additional Effect: High Enmity
Combo Action: Vicious Swing, Combo Potency: 200
3. Cruel Bite: Potency 100, Additional Effect: High Enmity
Combo Action: Devastate, Combo Potency: 320
Shadow Ward: Generates Darkness, duration 30 seconds
4. Sanguine Sword: Potency 100
Combo Action: Vicious Swing, Additional Effect: regain hit points equal to 100% of damage dealt
5. Exultant Swing: Potency 100
Combo Action: Sanguine Sword, Combo Potency: 260
Additional Effect: Increases max hp by 10% for 18 seconds, can stack up to 3 times
Shadow Ward: Generates Darkness, duration 30 seconds
6. Whirlwind: 80 potency attack to all enemies within 3y
7. Black Sky: 100 potency attack to all enemies in a cone in front of you
Combo Action: Whirlwind, Additional Effect: High Enmity
Shadow Ward: Generates Darkness, duration 30 seconds
8. Wrack: 50 potency Additional Effect: Target takes poison damage over time and has healing effects reduced by 50% for 18 seconds, potency 25
9. Dirty Kick: Target stunned for 2 seconds, off-GCD, 15 second CD
10. Blood Sacrifice: Lose 30% max hp to gain 25% DR; 15 sec duration; 120 sec CD
11. Body Pact: Increases defense by 50% and reduces magic defense by 50% for 10 seconds; 60 sec CD
12. Souleater: Increase damage by 50% for 30 seconds. Max hp is reduced by 30% for the duration of the effect. 120 sec CD
13. Cripple: Potency 150, Additional Effect: Heavy 40% for 20 seconds; 10 sec CD
14. Soul Pact: Increases magic defense by 50% and reduces defense by 50% for 10 seconds; 60 sec CD
15. Momentum: Increase crit chance by 20% for 15 seconds, every critical hit increases this bonus by 10%, 120 sec CD
16. Fearsome Challenge: Scream a challenge, increasing enmity against a target within 15y
Additional effect: 10% STR debuff for 18 seconds
Reaver Class Traits
1. Enhanced Vitality I: Increases vitality by 2
2. Enhanced Vitality II: Increases vitality by 4
3. Enhanced Vitality III: Increases vitality by 6
4. Enhanced Blood Sacrifice: Reduce loss of hp for Blood Sacrifice to 15%
5. Enhanced Souleater: Reduce max hp loss to 15%
6. Enhanced Exultant Swing: Increases duration of Exultant Swing to 25 seconds
7. Enhanced Fearsome Challenge: Increases duration to 30 seconds
8. Enhanced Wrack: Increases duration to 30 seconds
9. Enhanced Momentum: Reduces cooldown to 90 seconds
10. Enhanced Body Pact: Reduces magic defense loss to 25%
11. Enhanced Soul Pact: Reduces defense loss to 25%
12. Soul of Darkness: Increases Darkness's increase to enmity to 50%
Dark Knight Job Abilities
(GLA and MAR as secondary classes)
1. Consuming Darkness: 150 potency attack to all enemies within 5y and regain hp equal to 50% of damage dealt, consumes Darkness
2. Shadow Ward: Reduces damage by 20% and increases enmity; increases magic defense, parry chance, and parry value by 30%, while Shadow Ward is active, some abilities generate Darkness
3. Endless Night: Instantly grants Darkness, 30 sec CD
4. Onyx Wave: 300 potency attack, consumes Darkness
5. Ebony Shield: Surrounds you with an absorb shield that lasts for 30 seconds, potency 100, based off of attack power, deals damage to attackers while active, potency 50, 30 sec CD, consumes Darkness, off-GCD