Ok, think I fixed it. Found a hint on the Eidos Techical page, http://forums.eidosgames.com/showthread.php?t=119698
This tip is for people with fuzziness / blurry graphics for those with DirectX 11 enabled. Turns out Stereoscopic 3D is enabled even though “redded” out, yet it can still be adjusted via the slider...
They're actually trying to help people not
using stereo 3d, but it made me think perhaps stereo might be active even though it appears disabled. Turns out in DX11 this is the case, the problem was post processing.
So if I tick DX11 and untick post processing on the setup program, I can access the 3d stereo options in-game and it seems to render ok, so far.
DX9 doesn't work with or without post processing.