The Eternity Vault developer walkthrough provided some gems for budding Assassin and Shadow tanks out there. First up, and best of all, the specific details of Dark Charge are glimpsed;
Dark Charge

Very nice. The healing component feels fairly underwhelming; 31 HP every 1.5 seconds is a small amount of recovery for a tank with 12.5k health. That said the armor boost (150%) and threat generation boost (50%) are both very nice. The surprise, however, is the additional 20% increased shield chance, which when combined with Dark/Dark Ward gives our class an additional 35% chance to shield incoming damage. It's a little odd to see that it's a ranked spell, but I guess the ranks are there to increase the healing throughout the levelling process.
Discharge

Discharge has been mentioned on this site before (and can be found in the tanking guides section), but it's nice to see it in-game to confirm it's effects. It does indeed deal AoE damage, and perhaps more importantly the ability is confirmed to debuff the targets it hits, reducing their chance to hit by 5%.
Force Pull

Uses the force, Luke, to draw the target in, instantly pulling it to your location and generating a high amount of threat. Again, lovely to see it confirmed. The fact that it does not work against targets in cover was expected (and needed for PvP balance). The threat generation component is interesting; the ability does not state that it forces the enemy to attack you, just generates additional threat... so it's reasonable to assume that if the player being targeted by the enemy is still higher on it's threat list, even after the pull and the additional threat is applied, the enemy will continue to move away from you. The 45 second cooldown feels reasonable; neither excessively long nor spammable in PvP encounters.
Mind Control

It's our taunt. It forces the enemy to attack you for 6 seconds. A player target will deal 30% less damage when attacking players other than yourself; this is 20% lower than the previously expected 50%. The player PvP debuff also lasts 6 seconds; less than half the cooldown time.
Overcharge Saber

Provides a short-duration buff (15 seconds), scaling damage dealt by Lightening and Surging Charge by 100%, and more importantly for tanks, the healing component of Dark Charge by 300%. The two minute cooldown and low cost make it useful in PvE for those situations that need just a little more survival and self-healing.
Shock

Shock has a short cooldown with a relatively high Force cost. Through a talent in the talent tree called Induction (Assassin) and Particle Acceleration (Shadow) you have a 50% chance to reset the cooldown of Shock when attacking with Thrash and Lacerate (Shadow: Thrash and Lacerate). It can be used at range, which is particularly useful for picking up spawning enemies and trying to finish off a fleeing player in PvP (especially when combined with Lightening and it's movement slowing debuff). Shock will be particularly important for Assassin and Shadow tanks as it's damage and threat are increased through points spent in our talent tree.
Thrash

A single target attack that strikes the enemy twice, dealing good damage. Given it's cost it seems to be interchangeable with Lacerate, and provides solid single-target threat. Thrash/Thrash has a 50% chance to reset the cooldown of Shock (or Shock is you're playing a Shadow), thanks to a talent in the third tier of the tree called Induction (Assassin) or Particle Acceleration (Shadow).
Lacerate

Lacerate/Lacerate is an AoE attack, causing damage to all nearby targets. Given it's cost it seems to be interchangeable with Thrash/Thrash, and provides a nice AoE threat. Like Thrash, Lacerate has a 50% chance to reset the cooldown of Shock (or Shock is you're playing a Shadow), thanks to a talent in the third tier of the tree called Induction (Assassin) or Particle Acceleration (Shadow).