Originally Posted by StarsRPD
We all died on Heroic and still got it. I think you just need to complete the mission on Heroic. Edit: I read on TA it might have to do with not activating the orange buttons after the defense.
After reading this I also decided to give matchmaking a try for this achievement.
I also unlocked it - however everyone had at least one death, though both of the generators were both still running.