RESOLVED –
not sure what I changed, Vorpx was not working for me at all . I tried everything – disabling overlays (steam, nvidia), antivirus, etc. as directed in the “READ ME FIRST” section and I couldn’t get Dark Souls or Dragon Age to run anymore in virtual cinema mode at all.
Then last night I fired up Dishonoured and it hooked (and looked better than every before, the tracking seems a lot better). Ever since then Dark Souls has been running fine and messing about with the 3D FOV slider has improved it even more.
Hurray!