GL-AR750 USB Tether slow

I am tethering to a MiFi 8000 from my GL-AR750. It connects right away but is slow on the internet (10 Mbps down). I can get 60-70 Mbps down when connecting to the MiFi over wifi directly. Why would the USB connection be so slow?

USB tethering on the router is slow.

@alzhao Are you saying that this is a known issue? Is there any fix?

Max tethering speed is like 30mbps. But it really depends on phone. I think the driver is not so great.