So… I tried the DX12 version for the first time in a long while, it looked just fine. However, both the benchmark and the actual game had this glitch: in the benchmarg every 20-30 seconds where everything would be cut for half a second, I presume that there was simply a rendering pause. The game itself had it happen less noticeably, but in a horde scene on the Skittergate, on the plane after the standard ammo box after the boss, it went down to the crawl with some enemies teleporting.
I switched back to DX11 and it seems that the issue remained, although it was a lot less noticeable.
It looked like that during the worst part of the Skittergate, otherwise a lot more bearable. In the meantime, I’ve reenabled DX12 and played a couple of games without those issues. Well, tried to play a couple of games, it’s getting really hard to find reasonable coop on qp.