my system i5- 3450 @3.10ghz, GTX 560 1gb DDR5, 8GB RAM

diablo setting Display full screen 1920x1080 , texture quality HIGH, shadown MEDIUM , physis HIGH , clutter display HIGH , anti aliasing TICK, Low FX UNTICK, letter box UNTICK, Vertical SYNC TICK, max foreground FPS 150 TICK , max backgroup FPS 8 TICK

i feel spike whenever i attack. can anyone help?