There are a lot of variables when talking game performance, but when you add online game performance, it gets a little crazy. If you want to check for the weakest link, try reducing graphical settings and see if performance improves. Also, depending on where you are taking these measurements and what you are doing at the time, performance will vary. Very 'busy' or complex areas will run slower than sparse ones. And finally, if you have vsync on it will reduce your FPS to whatever your monitor's refresh rate is. For example, if it is 60Hz and the card could do 100FPS, then it will reduce to 60FPS. If you drop to 56FPS though, then vsync will take it down to 30FPS (which could be your 31FPS). Check both in game settings and in Catalyst Control Center to see if this is on or forced on.