It seems that an update on 1/18 dramatically reduced my performance. Prior to this, I was able to run on Ultra settings with ~30fps. Afterwards, ultra and high run at ~12fps, medium at ~16, and only on low do I get back to 30. Additionally, I've noticed two/three times now my graphics performance starts to chug so horribly it turns to about ~3 frames per minute. This persists for about five minutes, at which point I get a loading screen which mostly alleviates the problem (but I get affected by the flicker bug). I have an NVIDIA GeForce GTX 570, Intel i7-2600K CPU @3.4GHz, Windows 7 64bit, etc.
Well, helped a tiny bit (the mostly-high that it defaulted to is now at 16fps), but still not where it was. Thanks for the suggestion though! Edit: The problem appears to be in the "Graphics Settings" option (and, to a lesser extent, shadows). If I have that on high, I get the 16. That on low (and everything else on high) (except shadows, as mentioned), I get the 30. Changing shadows from low to high drops my fps by about 6 with graphics settings on low, and by ~1 when graphics settings are on high.
