Something I've noticed with Diablo 3, is that if you have Vertical Sync turned on, it limits the FPS to about 30, but if it's off it caps at 60 FPS. But for me, aside from server issues, I've had no issues at all running on my computer at max settings
Sager NP9370
256GB Samsung 840 Pro SSD + 750GB 7200RPM Secondary HDD
nVidia GeForce GTX 680M 4GB VRAM
Intel Core i7-3630QM 2.40GHz
16GB RAM
Mouse: MadCatz R.A.T. 7
Keyboard: Razer Lycosa Mirror
Additional Monitors: 24" 1080p Insignia LED/LCD TV and 21" Acer LCD Monitor
Windows 7 Ultimate