Filmed via FRAPS@60FPS
Song: The 'U.N. Owen' is her (studio version)- 隣人
Item Level: 731
Mirror of the Blademaster required.
Shadowstep required - Timing needs to be as precise as possible.
Marked for Death - This is primarily to help with the Anima Golem. Keep in mind this will reduce overall output on Dark Animus.

Things to note:
Anima Golem take 90% reduced AoE damage which includes the Explosion effect from the Legendary Ring, Soul Capacitor and Mirror of the Blademaster's Mirror Images. I could have used the Legendary Ring a little more intelligently. This would mean using the ring towards the end of the fight and then forcing FULL POWER by killing the last Golem before it explodes therefore dealing full damage rather than 50%.

Boy oh boy.

This was a bit of a struggle since I decided to take a more brute force approach rather than the conventional strategy of using Burst of Speed/Shuriken Toss (See Shiekrunner's H Animus kill) which is a lot less of a headache than what I've done here.

I took this approach because I like this boss. A lot. Nevertheless detail time.

There aren't very many changes to this boss on Heroic since even on normal this encounter is very punishing on mistakes but, it is still good to know what is even scarier on heroic.

Going Step-by-step:

Upon bursting the Anima Globe 48 Anima will be transferred to the Anima Golem (small add) and 52 will transfer to the Dark Animus (Boss). This means that we will have 12 Anima Golem and one Dark Animus. Dark Animus being active from the start of the fight is one of the major changes and will affect the entire way this fight is done.

Now, this beginning phase requires a bit of luck and execution.

Once you have all twelve Anima Golem and one Dark Animus chasing after you use Mirror of the Blademaster on Dark Animus (I used a focus target macro) the plan here is that we need 1 (exact) of the Anima Golem to get hit by the Mirror Image and thus having aggro on it as opposed to yourself. The reason we need exactly 1 is because this means that it will NOT gain the Accleration Link aura which increases the damage it deals and it's attack speed by 250%.

Dark Animus' Anima ring ability is still incredibly dangerous but on Heroic it is even worse. If you get hit by an Anima Orb not only do you take 200% increased Physical Damage but you will also take 21,600 Fire Damage over the duration. This is where Shadowstep is needed. Shadowstep will take you directly behind the Dark Animus' hitbox meaning you will safely avoid all of the Anima Orbs (the CD of Shadowstep is going to be cutting it close so keep that in mind).

Spawning the Mirror Images means you have roughly 20 seconds to kill the rest of the Anima Golem. Once you have killed all but one of the Anima Golem Dark Animus will have exactly 96 stored Anima

With 96 stored he will not cast FULL POWER! until he has used Siphon Anima (I am not 100% sure if this is cast at a % of HP or timed based).

At this point this fight becomes very managable. Continue to avoid the Anima Orbs, and if needed stall as best that you can so that once he casts Siphon Anima you have burst CDs available to finish him off. Remember to hold Cloak of Shadows for Full Power. Additionally a better way to use Cloak is to wait for a few hits from FULL POWER and then use it. Additionally Feint reduces the damage from FULL POWER.