I used to have DP daisy-chaining (since my SP2, by the way), but I eventually just recently abandoned it with my SB.
I have 3 external monitors, all 30" 2560 x 1600 Dells. I have never understood why Windows would never recognize a 3rd monitor and I have always had to use USB for the third monitor, instead of daisy-chaining.
Though I thought all such issues would be resolved not only with Windows 10 (which was proven not to be the case when I upgraded to Win 10 on my SP2) but definitely with the SB; however, that was also proven not to be true.
I have since given up and settled to use two of my externals using the two DP ports on the Surface Dock and the third monitor using USB. I'm still running into issues, but as of right now, things seems to be a bit
more stable not using daisy-chaining, but just a bit
This is all extremely disappointing and frustrating.