with ' no joy ' at this point I'd swap over to a PC and rebuild a fresh download of BFG and include KNC, disable OpenCL enable CPU.  The last 2 are just to make sure you have the full pack downloaded and all dependencies.  once built, only 1 in a USB port ( part of troubble shooting is try 1 device at a time due to power restrictions ) DIRECTLY on the PC.  A front pannel connector directly to the motherboard is a wonderful thing!  IF it does work ( ' sudo BFG etc, etc ' ) remove it while it's running and swap to the same USB port the 2nd Nano.  BFG should try and re-enable ( done this with ANTMiners and Erupters to find dead/underpowerered USB ports ).  Assuming this works, it's a matter of doing it all again on the Pi ( with out the CPU enabled ) and trying there.  I've had to open USB hubs and bypass Zeners, regulators and a few other ' power tricks ' that would limit the 5V line to 500 mA per port.  I don't have your hub so no clue what/if it does for voltage regulation that can also cause this issue. 

One ' trick ' I have in my list of things to do with powered hubs is find the 5V line from the pc ( or Pi in your case ) and cut it to prevent power issues and to ensure the powered hub IS getting power from the brick.  I can never say this enough, share the ground plane, separate power for the miners so power isn't getting used for more than the miners and you can tell what bricks overheat.

May the force be with you.