No, it's not normal, there must be something wrong. Check this:
CPU speed = at what speed is your CPU running ? Is turbo mode enabled ?
Visibilty (view distance) = lower the better (i'm using 1600)
Video Memory = set to "default" to use full video memory
Anisitropic Filter = impact > low
Anti Aliasing = high impact > low
Postprocess = high impact > off
blood = low
Your rig looks a bit more powerfull than mine and i'm running A2AO on "very high" (AA,AF normal) at 1920x1200. With Vsync on, the FPS usually are between 30 and 60 (max).