I'm also experiencing atrocious performance since the patch. The night before I updated I had buttery smooth gameplay with every graphic setting maxed out. Now I stutter constantly - it is a complete slideshow. CPU spikes to 100% almost constantly. I have tried all of the troubleshooting steps listed here - cleaning out the Origin cache/temp files, clean boot. I don't have Intel Rapid Storage Technology on my computer so that isn't the culprit.
Given that I had 0 issues prior to the patch I would suggest it's something to do with the patch, not a problem with my PC. I'm honestly getting pretty disgusted with this. I have never had the experience of a mandatory patch completely killing a game before - especially when it's a (mostly) single player RPG (which I forked out $60 for and hardly got to play..). I'm getting to the point where I might have to look get a refund. Very disappointing. :/
For what it's worth, here is a pastebin of my dxdiag report. http://pastebin.com/6XbhqcAP