We replied to Dan via our private email ticketing system. (Dan, we never got a response, so if the email wasn’t received or you’d like it resent, please email email@example.com and we’ll be glad to resend!)
Posting the response here for the benefit of others who might encounter this thread while doing research:
Usually the type of behavior you’re describing is caused by interference between the wireless network adapter and the USB 3.0 controller on dock, as both devices operate in the 2.4GHz spectrum (as do microwave ovens, cordless phones, wifi access points, baby monitors, etc). In situations where the wireless router is very close by and the signal is at full strength, it usually doesn’t affect the speed by any noticeable amount. However when the signal is already a bit weakened by the access point being on another floor, there can be enough interference to notice a speed decrease.
In many cases the issue can be somewhat minimized by experimenting with the dock in slightly different positions on the desk.
Also, if your router and network adapter support it, setting up a wireless network that operates in the 5GHz spectrum (rather than the 2.4GHz spectrum) can sometimes help reduce interference. However, the 5GHz range is more susceptible to signal reduction due to walls and other obstacles, so it’s not a certainty that it will help with overall throughput.
Apple has a pretty good article up regarding potential causes of interference, if you’re interested: