Hi, The virtual usb nic is used by the idrac to communicate with the OS, disabling it is fine if you don’t need the iDRAC to communicate with the OS.
We have iDRAC7 Enterprise on two new NX3200 NAS with Storage Server 2012 R2 . In the OS a NIC shows up in Network Connections with Device Name "iDRAC Virtual NIC USB Device" that is grabbing a DHCP address. Can someone explain what this is? I disabled it and iDRAC still works. Thank you  
Server 2012 R2 iDRAC Virtual NIC USB Device