Focusrite currently don't support Thunderbolt-3 for Windows.
In short, that means you don't have "PCIe via Thunderbolt" support (needed for PCIe level performance).
We now have full "PCIe via Thunderbolt" under Win10 (if running one of the latest Z170x or X99p motherboards that offer Thunderbolt-3 via USB-C port). You also need a USB-C to Thunderbolt adapter ~$84.