FPS drops after season update

Is anyone else's performance tanking since the new season?

I used to get a smooth 170 FPS, but now I'm hovering around 120 and sometimes it just dives to 40-50 FPS. I've already tried everything, including a fresh install of my OS and the game, but the issue is still there.

Talked to my buddies, and it seems like the people with Intel CPUs are the ones getting hit the hardest. The AMD guys seem to be fine.

Seriously, how is a game this old getting negative optimization? Just wondering if this is a widespread thing or if we're just unlucky.