I seem to be in the same boat as you. Same processor and RAM but graphics card is Radeon HD 6520G, updated driver to latest. While I don't get framerates that low and my connection is usually around the 100-200 ping it's still quite bothersome. It happens more on co-op play especially when there is a huge mob and lots of action going on. Changing from high to low graphics also has little effect on performance.I'm not having connection issues, but still wildly fluctuating FPS - avgs 12-15. It's terrible.
I have yet to play this game smooth in the 2 days ive owned it.
It can't possible be my rig, can it?
Intel core i7 CPU Q820 @ 1.73 GHz
6GB Ram
GeForce GTX 260M (1024MB GDDR3 dedicated video memory)
Latest driver (296.10)
Doesnt matter if I put it highest or lowest settings, pretty much same result.
When there isn't much going on and I am playing solo, I get smooth as hell framerates and game play. Act 1 and Act 2 were solid but Act 3 has so much stuff going on in the environments and the more complex mobs plus of course better, more spammy skills unlocked.