Yeah, I know it's confusing that Win8 (and Win7, and even Vista with an add-on) supports DX11, and DA2 supports DX11, so the game lets you choose it as the Renderer even if your hardware can't handle it.
But... If you don't have DX11-capable graphics card one of two things happens. If, (as for you and me) you had a DX10/DX10.1 card then mostly you just get a static image in the places where a true DX11 system would be showing some sort of motion/flickering/etc., and a DX9 card might just show a black screen.
In DA2, all of the repeated "Area Loading" screens are of this sort. The swinging sign as you enter the Hanged Man, the liquid gold filling the Kirkwall crest mold as you enter the Vicount's Keep, the bas-relief of the line of slaves as you descend into Darktown. These have lighting and animation effects that require DX11 to display properly.
And in the worst cases, you get a total freeze and/or crash to desktop!
When I first discovered this I ran out and got the best DX11 card my poor old gaming rig could handle. (Which isn't much. Power supply and physical space limitations in the case required a true single-slot card. I went with the nVidia GT640.)