Hello Paulledot, this is how my guild completed the fight:
2 Tanks, 3 Healers & 5 DPS. This is a safe composition, as long as your 5 DPSers do atleast 75k-80k DPS you will be fine.
What we do is we completely fill up 1 Massive Anima Golem, that requires 9 Small ones, By the time we have killed 9 Golems, we have 3 left. Whilst we were killing the first 9 Golems into the Massive Golem, our DPS DK taunted out 2 Anima Golems from random raiders, and put those into a Heavily Damaged Large Anima Golem (Big one with electricity around it).
By the time we were done with that, we have 1 Anima Golem left, to activate the boss with. Once activated, its all about nuking. When Dark Animus comes alive, pop Bloodlust, Potions and all DPS CDs to bring him down. With this strategy he will get 70~ Anima very Quickly, but after first engaging him, you will have 180 Seconds to kill him (3minutes), which is more then enough (i think he had 82 Anima when he died).
So all in all, quite simple. Get 9 Small Anima Golems into 1 Massive, 2 Small Anima Golems into 1 Large Heavily Damaged, Then Activate the boss and kill him. Just practice his 25/50/75 Anima Abilities and you'll get a kill within 10 tries.