Guild Wars 2

The only thing that i still do not understand, is why GW2 requires both even without much graphic, for example I play battlefield 3 in high quality with 50-60 fps,
but thanks for all your answers!

http://www.hwcompare.com/8891/geforce-gtx-560-ti-vs-radeon-hd-6850/

no many differences

so What i need to change to play with a nice fps , ,change my videocard?

it says 256 mb shader 3.0 in minimum requeriments , i have 1gb 5.0shader :/

I have a computer with the following settings:
AMD FX6100 3.3GHz 6 CORE
RADEON 6850 1GB GDDR5
8GB RAM

and im playing with 40 fps, theres something wrong?
 
my computer spends a lot of minimum requirements!