I'm sitting on a mid-low range rig right now.
AMD FX-6300, 3.5ghz
GTX 660 Ti 2GB
8GB DDR3 RAM
etc.
This thing handles games like Borderlands 2 and Diablo 3 with few issues; I've thrown Battlefield 4 at it with pretty great results, too.
However, in D: OS, once I get into town or a larger battle I routinely stay at 20-30 FPS, regardless of whether or not I have the game set to ultra settings or low. Is there something I'm missing? I have V-Sync turned on, but that's because the tearing gets HORRIBLE without it.