If you're convinced that it's not an app you installed, if you've done a SBF flash and cleared the cache along with it, and things are still problematic, then it sounds to me like it would be hardware related. A SBF flash and clearing the cache will get you to as clean of a point as the phone can essentially be on the software side of things.
Yeah I was reluctant to do this update when I saw some people having issues with it, but I sbf'd back to stock and did the two upgrades. It has been great for me I have not rerooted yet and still have all the factory apps except NFS. Battery life has definitely improved I am 10 hours in and only down to 90 % left, seems weird you would get worse from going to it if you sbf'd and restored to factory. Might be time to pay a visit to a Verizon store and see what they say about getting you a new one.