Not that i'd make enough difference to cause WOW to run slow but it's obvious you aren't using your RAM in a dual channel mode. You should match your ram sizes and speeds so you system can access 2 DIMM's at the same time. If they are not matching dual channel mode is not available and thus, your system runs slower.
I would use driver sweeper to flush out all of your old driver files then do a fresh install of the newest drivers from AMD.
Also, Your connection speed could be the sole cause of slow gameplay, especially for a game like WOW which is played 100% online only.
Update: Your connection speed is fine. You might want to try a traceRT to the battlenet servers and make sure you connection to them is reasonably fast.
Aside from all that, some of the worst slow down happens when windows is doing updates OR if your virus scanner decides that scanning while you play a game is a good idea. Make sure all windows updates are complete and that you don't have a virus scanner or something else running in the back ground slowing you down.
Because based on your system specs, you should be able to max out WOW.