when i did the pre-patch for MoP, the game crashed: black graphics, blue screen, computer froze, etc... i was in the beta and had no issues. they definitely added something to the live MoP graphics.
i posted on the tech forums and put in my dxdiag text. i wasn't the only one. lots of people had their graphics go stupid with the MoP pre-patch. i run it on a core2 duo laptop. i noticed in the tech thread, there were even people with i7 cpu's posting the same issues. the response we all got was: "update your video card driver" or "your video card is no longer supported."
how i fixed my particular issues on a core2 duo, 6gig ram, HD4650 graphics was to enable v-sync, low shadows and low water. runs fine now and i can do maxview without any slow-down (if my setup has no issues with maxview, your's definitely shouldn't). anyways, some of the guys also posted saying that going back to dx9 also helped them. something to try.