Heroic: Omnotron Defense System

On heroic, Nefarian will periodically mess with one of the abilities used by the Omnotron Defense System.

Magmatron: The player marked with Acquiring Target will be rooted, meaning everyone else needs to move to avoid the flamethrower.

Electron: Transforms the lightning rod into an AoE that hits the entire raid, dealing less damage the closer you are to the affected target.

Arcanotron: Turns a power generator into a bomb, causing it to expand, then detonate in a large explosion that encompasses close to a fourth of the room.

Toxitron: Warps the raid into the center of an existing chemical cloud, which can potentially cause a wipe if poison bombs are out, and happen to be in or near the cloud at this time.

On top of this, Arcanotron's Arcane Annihilator does more then twice the amount of damage it does on normal ,meaning it absolutely needs to be interrupted, and the energy for each of the golems decreases around twice as fast as on normal, meaning you'll be switching targets a lot more often, and the abilities used by them can potentially overlap in ways not possible in normal mode.