Buy the "A Flip Of A Coin" DLC for $1.99 or as part of the season pass. Then go to Arkham Episodes.
Here's some steps to get through this as quickly as possible.
Take out the Signal-jamming guys with the antenna backpacks first so you see what's going on. The rest is standard predator tactics.
The second room is tricky, go under through the grate and all the way to the breakable wall, spray it with explosive gel and detonate to take out the gattling gun big guy, then head back up through the grate and step on the rope to be directly above the guy in the middle aiming his gun at the taken down big guy.
USe your hacker device to disable the farthest sentry gun, then carefully time yourself to to a fear takedown on your guy below and quickly the guy next to the disabled sentry gun. This may require some luck but when you eventually do it, quickly press Y to disable the other two sentry guns and then run to the fuse box and press A to destroy the wall and the last sentry gun. You have 30 seconds.
After that fight the guys and solve the puzzle, three human heads left and three demon heads right.
After that fight the last henchmen and press Y during a Two Face cutscene when he's flipping his coin.
Here's my video playthrough.