If you minimize the game with DX11 enabled(using windows key) it will never truly minimize into background. In my case I play with fullscreen mode.
This is kinda annoying if you use more than one monitor as your cursor is still captured and can't leave the monitor wich displays the game. As a workaround you may open some other windows(explorer, browser or something like that), klick into it, press the windows key again and your cursor will be finally free to move wherever you want.
This is something that can or most likely will get you killed if you have to tab out frequently in wvw.
I made a screenshot to show you, that my browser is just displayed above the game and it still replaced my taskbar.
https://images.justgalak.com/guildwars2/screen/dx_background_issue_1.png
Edit:
This issue exists in windowed fullscreen aswell, even if it's a little less annoying as it can't capture your cursor.