It's funny you mention that, I tried it on my StarTech dock, which is also DisplayLink, and it was much worse.
So, as of right now. I just returned my Surface Book... It was a hard and sad decision for me, because I really liked this machine. This USB thing was the last straw. I could live with the other more obvious software related issues with display driver performance, and even the battery life issue. But me not being able to properly use my USB drives did it in for me.
I'm really unsure if it's just a defect in my Surface Book. I suppose I could get another one to be sure... But I think I need a break from this machine. I've spent so many hours troubleshooting it, instead of actually working on it.
Such a shame. I've followed much of what you've written. I've had many of the same problems you've had.
I just came here to give you more input on my USB ports as both of my USB 3.0 ports have never had a problem. There's no reason to type anything more on that since you threw in the towel. I've not seen anyone else have a USB port problem like you had.
With the update from yesterday that fixed the Intel HD520 Skylake driver problem, I have no complaints on mine and I'm truly enjoying it. My battery life at 50% brightness is consistently between 10 to 13 hours. My color accurate screen at 3000 x 2000 is incredible for my photography with Adobe Lightroom/Photoshop CC. Of the dozens of computers I've had over the years this is the best one yet. I really do love my Surface Book.
Gary in Atlanta