Thanks for posting your question here. I’ll be happy to help. Isolating problems with transfer times can be a bit tricky, especially when there many variables involved. For a large transfer there’s the time for the data to be read, combined with the other disk usage of the computer that plays a major role.
If you want to get some raw numbers on each component of your setup to compare and possibly find the one that’s introducing a lag first get a disk benchmark program like ATTO.
Then run a test on the disk connected to a USB 2.0 port, a USB 3.0 port, and a USB 3.0 port with USB 3.0 hub.
To get a good perspective of the USB disk you are writting, compare similar data points from another USB disk.
If you see a big drop in transfer speed at any stage, you’ll have a place to start troubleshooting. My suspicion is however, if you were to connect a USB 2.0 drive to the same setup, or use a USB 2.0 cable somewhere in the chain you would see anywhere from 5-20 Mb/s so it may be more of an overhead issue and your USB 3.0 setup is going much faster but still not approaching it’s maximum.
I hope this helps.