I wanted to start this in a new thread, as it's more about an issue I have discovered with the Surface 2 and 3 USB3 port.
It appears that even plugged in, both of my Surface (2 and 3) will not power some external hard drives, reliably and there is problem in trying to power external DVD and Blue-Ray burners.
With the burners, they will attempt to be discovered, and the Surface device will see them, but as you start to spin up a disc, the burner drops from the Surface pro, since the port can't give enough power to run the disc. If you add either a powered USB2 or USB3 hub, all the problems go away.
My point in all of this, when you tether, to a IQ back, you have the option to charge the back, slow or fast. In the past, I have noticed some strange behavior when I have this set to any type of charge, and I think I know why. I believe that the power from the Surface 3 especially when only on battery, is not giving a consistent enough power/charge signal to the IQ back. When you tether, and tell the connection. NO CHARGE, then things for me go a bit more smoothly. I am sure that the IQ backs are looking for a pretty narrow range of power for the charging and since the Surface 2 and 3 are not really given a fully charged port, you might do some damage to the IQ back over time. I have no way of knowing this for sure, but the fact that the Surface USB3 port is running below the standard power output, does concern me.
Just a heads up to others out there tethering.