Degrading Textures?

Please read the entire post before commenting. The graphics in Dishonored looked really good, at least until I downloaded the latest patch. The characters now look like early 2000 polygonal blurs of color. The posters that plaster the buildings of Dunwal used to be crystal clear and are now indistinguishable blobs of color. Road signs are now illegible, and even the less interesting grey textures that make up the sides of buildings are obviously washed out. The difference between before and after is very noticeable. How do I fix it to get the good textures back for the XBOX 360?