Textures have blue holes in them.
Check for latest GPU drivers
Check cooling on GPU and CPU
Bout all most will say, those are usually the two cases causing that.
Definitely uninstall and reinstall the latest video card drivers. If that doesn’t work, get an app that can monitor your GPU and CPU temps and post them here (while comp is idle for 10 minutes and after running the game 10-15 minutes).
In another game (Skyrim if memory serves) a similar issue was caused by bad Anti Aliasing. You could try setting your graphics to allow games to determine correct Anti Aliasing and / or switch GW2 Anti Aliasing to native.
The other posters before me have given good advice too.
My next suggestion was going to be what UKnight suggested
The blue artifacts looks to be an AA issue. You can see that they appear at edges where jaggedness would pop up. Open up your video card control panel and make sure you do not have forced AA settings that will override ingame settings. I only have an ATI card so in my catalyst panel, I have everything set to use application settings.
The driver seems to be the latest version available. So i’ll try checking the other things as well. Anti Aliasing does seem a good idea, but oddly when i enabled it in game with the options screen it crashed. I think i’ll still try seeing if i can look at the video card settles in the control panel though.