What do you want DX11 for? What do you think adding support for DX11 will do for the game?
Well DX11 is capable of more fps while still producing the same graphics. By changing to DX 11 you get a significant performance boost. Also it allows you to add realtime tessellation which means cloth behaves like real life. It allows for better multi threading and also allows shaders to be used for non graphical tasks(helping to clear up cpu bottlenecks by allowing more cores to work and using gpu to help cpu). GW2 could benefit from a greater degree of multi threading as by all reports it doesn’t even load up all the I-7 core much less the new AMD 8 cores. Basically with my old WoW comp I saw a 20 fps performance boost in capital cities from switching to DX11 over DX9.