I played some Diablo 3 with my S3 running the build 10158. It ran pretty well. I noticed some very slight lag at times, but I think that was due to network congestion on my home network. I was using WIFI on my S3, but my Xbox One is connected with a cable. The connect speed test came back saying that my network speed wasn't fast enough, but it worked very well anyway (I switched it from 2.4G to 5G WIFI before streaming). I ran a D3 rift (about 15 minutes and lots of graphics) without any lag deaths.
I really think it will get much better since the Windows 10 graphics driver (Intel) in this build is somewhat flaky. It will reset itself from time to time. Actually, that's my biggest complaint so far running Windows 10 on the Surface 3.
Added Note: The aspect ratio is different for the Xbox One and S3, so there are black bars at the top and bottom. This would be true of the S3 Pro as well. Didn't cause a problem for me.