Quote from Planned Changes
Warlock/Knight
Heresy
Passive
Modifies Holy Strike to be Dark Strike, changes it to inflict 2200 dark damage, increases its range to 225 and adds 10 focus cost.
Dark Knight
Passive
Enhances Enhanced Shield to provide 100% physical defense instead.
Hatred
Cost: 30 Focus
Cooldown: 30 seconds
Increases your aggro by 186% for 12 seconds.
Dark Hand
Passive
Darkness allow you to wield a shield.
Lights Out
Passive
You don’t need light to find your path, doubles duration of Defense Net and applies it to entire raid with extra Fear immune, but blocks your sight upon use.
Darkbringer
Passive
Willpower Construct will increase your dark damage by 30%.
Denial of Death
Passive
Reduces cooldown of Life Weave to 3 minutes and removes its Psi cost.
Eliminate the Filth
Passive
Light isn’t there as long as you do not look at it. Surge of Awareness won’t decrease defense, Calm Paradox won’t decrease attack.
Hasty as the Night
Cost: 1 Psi
Cooldown: 60 seconds
Allows you to cast while moving and increases cast speed by 50% for 20 seconds.
Dreadful Sleep
Cost: 4 Psi
Cooldown: 60 seconds
Channel Time: 6 seconds
Only usable under effect of Willpower Construct. Puts enemies within 100 range to a sleep state*, interrupts their spell casting, inflicts 1600 dark damage and simultanously pulls them slowly towards caster. Each level adds to aggro.
Enemies can’t attack during this state.
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This is actually pretty cool, I think I see some similarities to my concept (LINK) but also some differences, but that doesn't matter, since you really brought us a magical tank with this! 
I think, overall this class should be a ton of fun to play, I definitely gonna test this out and maybe play it. But I still miss some decent things which should matter a lot I guess.
1) How should one be able to actually "tank" without plate armor? With just a shield, you need to build a very specific gear (cloth with defensive stats) for this, that can't be used for any other class (maybe K/M), which isn't worth it to me.
2) "Heresy" changes Holy Strike, so it looses aggro multipliers?
3) "Dark Knight" should also enable to use plate armor additionally and somehow transform physical crit into magical (and physical attack into magical).
4) "Hatred" with 12s duration and 30s cd seems a bit situative, maybe the duration could match the cooldown, like the knight's Hatred skill, so that it can be used more often, for a constant aggro rate.
5) "Dreadful Sleep" seems to be the only AoE aggro skill, which sounds pretty good as it is, but cd is way too high for using it more than only once in a pull. Also 100 range isn't that much, maybe you could add another smaller AoE aggro skill with a lower cooldown additionally? There are only 3 active skills, rest are passives, maybe some effects could be combines to get another slot for such a thing?