The second iteration of 2v8 is now LIVE - find out more information here: https://forums.bhvr.com/dead-by-daylight/kb/articles/480-2v8-developer-update

Is it a bug or feature that adrenaline doesn't instantly heal you after getting downed?

It's so unclear whether it's a bug or a feature for whatever reason it might be but afyer getting downed adrenaline doesn't immediately pick you up which makes it really easy for killer to just insta down you again. For once a game perk that doesn't even work in certain situations I would expect it to function properly.