My points have also gone back to the 4 thousands, sometimes low 5 thousands. I'm still running the 185.20 drivers. My theory? There were and still are some "exceptional" work units. I had one yesterday that drove my GPU temperatures into the 70s and was giving me ~6000 PPD iirc. That same GPU is folding at 56 degrees now and giving me 3600 PPD according to FahMon. I don't remember what project that was but I'm seeing large variation even within a project, say a pair of 5904s.
If you read the descriptions over on FoldingForum, they say all the 590X series WU's will have large variations in frame time within the WU. They are often consistent for a long time, but then have random frames here and there that either complete very quickly or very slowly. IIRC they said variation of 50% is considered normal from frame to frame, but over the course of the whole WU, it should still achieve a normal average of something like 10% from WU to WU.
Right now there's two main WU's for the nvidia side, and the easiest way to tell them apart is by what core they use. You'll see this in the log file for FAH. If it loads fah_core11, it's the older style, probably a 768-point WU and you may see anywhere from 5400-6000 ppd and it should run a steady, very high temperature. The fah_core14's are now worth 1888 points and will fluctuate more. I've seen 4700-5400 ppd reported on a frame by frame basis, averaging out around 5200 ppd for the whole WU most of the time on those guys. Temperatures are significantly lower with fah_core14 WU's than fah_core11 WU's.