This solution is simply to inform of the differences between Normal and Heroic so i am assuming you know the basic mechanics of all the encounters.
Recommended Light: 380, 390 by Aksis phase 2.
General
- No revives other than Sunsinger self revive
Vosik
- Takes 6 Siva Charge throws to get to a monitor sequence. They do still need to be thrown in a small time frame.
- Different monitors will turn on than before. They are still left, right, and middle, but are larger and take more damage to turn them off
- Clean Room doors are partially closed, slide to get in
Siege Engine
- After killing Meksis, the Siege Engineer atop the Engine, a Spider tank will spawn in front of the Engine's ramp.
Aksis Phase 1
- Siva turret on left, right, and center
Aksis Phase 2
- Now takes 7 Servitor kills and Siva Charge throws to take down his shield and start the teleport/empowerment/damage sequence.
Same as with the previous raid achievements, I can also confirm that you only need to defeat Phase 2 of the Final Boss for the unlock.