GW2 Graphics
When I play on 3D mode the exact same thing happens. Setting “Shaders” to Medium removes the black ground. I’ve seen this problem a while ago, so i think that’s a common thing and they won’t fix it soon.
To avoid the forced 3D: try to turn off 3D in your driver settings befor launching GW2. Sometimes it bugs on my driver when I use 3D and I have to enable/disable it again