Open Diablo 3 shortcut, on the tab that says shortcut search the Target, it should say something like:
"C:\Program Files (x86)\Diablo III\Diablo III.exe"
Change that to look like this:
"C:\Program Files (x86)\Diablo III\Diablo III.exe" -launch
Now when you double click the shortcut it will launch the game without the Battlenet app
