I have the same problem - my carl9170 based devices do not do promiscuous mode.
We are not the only ones who have this problem:
http://marc.info/?l=linux-wireless&m=142551016732296&w=2
and it has come up on ask.wireshark.com:
https://ask.wireshark.org/...
We are not the only ones who have this problem:
http://marc.info/?l=linux-wireless&m=142551016732296&w=2
and it has come up on ask.wireshark.com:
https://ask.wireshark.org/...