If you're down to follow, this is how I got Doorman working in the meantime. Hopefully they update him soon.
Open Steam's developer console, can type this in a browser to open:
*steam://open/console*
Type "*download_depot 1422450 1422452 3003774953827025839*", this will download the previous version of the specific files that got updated. You'll find them in "*"Steam\steamapps\content\app_1422450\depot_1422452\game\citadel\bin\win64"*"
Just in case they were dependent on each other, I took *client.dll*, *host.dll*, and *server.dll*, and replaced them in Deadlocks *citadel\bin\win64*
(if you ever wanna revert the changes, either keep a backup of the original files, or just verify game integrity.)
NOTE: I don't know what other changes were made in these files this update so who knows what you could run into. All I know is it resolved my performance issue with Doorman and I've been able to play multiple games without issue.