After testing, here's my opinion on Ruin.

Unfortunately, it all comes back to what I thought it'd be. It's a midgame Hex perk, and will only really be good at killers with good early game (such as Legion who can keep multiple survivors mending while the gens regress) or killers with great defensive setups (such as Hag and Demogorgon).
Is it balanced? Yes. I think so. Is it useful? With the right combination and strategy, yes. How will this affect the game? It will definitely influence my personal playstyle to be more strategic and careful with my early game, but what about the casual players?
A lot of people in DBD seem to forget: this isn't some Dark Souls game where you have to improve and be careful with every single move. DBD is a casual game, and without serious improvements to ranking system and completely taking all RNG out of the mix, it never will be competitive. Telling players to "git gud" might tick them off, because they may not want to improve. They may just want to chill out with some DBD after a long day at work, but the stress of gen time could drive them away. As an avid player of this game, I never really play it like that. I play to improve, as I'm sure most people who take this game seriously do. But, what of the people who just want to play Michael Myers because they're a fan of the movie and not have to worry about "applying pressure" or "gitting gud".
The problem with this, however, is balancing around this relaxed style of play will give the higher tier killers easier tools to work with to be even more efficient. I'm at a loss, I'm not sure whether the change is good or not. There are definitely alternatives to Ruin and some killers don't even "need" it to play at max capacity at all. Anyways, unlike a lot of people here, I will continue to play killer because I never really liked Ruin anyways. I won't slug excessively or use cheesy tactics like NOED like some are saying they'll do, cause hey, survivors can have fun too. I just really hope they'll address the stress test killer is right now, and give them some early game tools that won't be abusable but take away some of the stress.
I'm actually a massive fan of this PTB, BHVR give your art and sound team a raise! It's incredible. New Doc I think needs a tad bit of tweaking, but overall a pretty great change.