The Surface Pro is billed as being able to "play Diablo 3 on the game's high settings without compromising on performance." This is a lie. If a large part of your criterion for a mobile device is, "Can it play D3 on High?" then buy a gaming laptop because you really can't PLAY on High.
You need to lower the settings and compromise on resolution to get smooth graphics so that you know where your mouse is. Playing for longer than 20 minutes kicks on the backup fans. The tablet gets HOT (and we all know heat and technology don't get along well). It is for these reasons that I don't recommend using the Surface as your primary vehicle for playing Diablo 3; however, it can run the game smoothly at moderate resolutions and low/no effects. Good for random grinding, bad for enjoying the experience.
With that being said, here are the settings you need to enable to get the most out of your Surface for Diablo 3:
So there you have it. My two cents on what you need to play Diablo 3 on the Surface. As I said above, it isn't the fastest gaming mobile device in existence, but it CAN play the game... just not with all the bells and whistles that people have said it can. Some people who write should honestly talk to real people before they put words to paper.
Aside from those gripes, the Tablet has stunning displays, and is great for my collegiate notes. I would recommend the product to others one Microsoft fixes a few key issues... which I won't discuss here.
Best of luck to you other Surface Pro users out there.