It is the AA. You can turn it off altogether to see what that looks like. Just change the AA in your post-processing volume between none, FXAA and temporal to compare. For both FXAA/TAA you can change the number of samples it does. More samples generally means cleaner edges, but more blur. You can change this dynamically at the console with r.PostProcessAAQuality [0-6] 0 = off 6 = most samples. These are both full scene AA techniques, they will AA both edges and textures/materials, but at the cost of a general blur.
The nvidia multres shading and gameworks branches are essentially various techs for things related to physics and VR performance (multi-res shading), but generally won’t interact much with the blurriness you speak of.
Moving to a forward renders that uses multisample AA (MSAA) will help make your VR more crisp by just AA edges (but leaving the potential for specular and material aliasing). There are currently two branches for this: the oculus branch which is very different that the standard UE rendering path, and the Epic forward render coming in 4.14 for PC (mobile is already a forward render). The oculus fork has some limitations about numbers of lights, etc. I have found, in my limited time with it, if you just load up an existing project it will visually differ quite a bit from the standard deferred UE render. You will likely have to commit to the oculus path and tailor your art to match. The other option is the official forward render for PC that is currently being worked on by Epic. A really, really rough version is hidden in 4.13, but will see its first general release (likely as ‘experimental’) in 4.14. It doesn’t appear to have the same limitations and generally I’ve found the visuals match the deferred render more than the oculus fork does.
No perfect solution exists for AA that removes all jaggies and aliasing without impacting the crispness of the image