New Ruin is fairly good on Billy
Perks: Hex Ruin, Surveilance, Hex Thrill of the Hunt, and perk of your choice
Addons: Doom Engravings and Carburettor Tuning Guide
He benefits off of new Ruin fairly well since he has very high map pressure. The information from Surveilance + Ruin + Thrill of the Hunt gives him enough information to always be in a chase. Removing the need for him to kick generators further increases his pressure while slowing down the game. Ruin + Surveilance is also fairly handy for the very immersed survivors that run away at the sound of your Chainsaw. He can defend his totems very easily with his movement speed.
Comments
New Ruin is good on all high mobility characters. Billy, Nurse, Spirit, Oni, and Demo, since you can apply pressure all over the map. It's ironic, since it's low mobility killers that need Ruin to work for them, not high mobility.
Crack Billy and ruin is just a little too disgusting to use imo. It is a build you use if you wanna win though.
Ruin + Surveillance is also good on stealth killers with hit and run tactics; Wraith and Ghostface.
Billy and Demo are really the only ones that can defend the totems very hard and effectively though. Oni can but if his power is out, he cannot defend them. Spirit is not fast enough in my opinion. I have not tried it on Nurse but with the blink cool downs I am unsure.