Maybe this will help--or not. I have been able to access an SD card via OTG connector and card reader. It's been a fickle set-up. This is what seems to work for me.
Rooted stock 4.4.4 + Stickmount Pro (haven't tried it without but will in a bit). ATM, I'm on 3.4.0 ElementalX but usually run Franco so I don't think kernel has any effect. Connect all hardware--card in reader, reader and OTG cable, OTG to N7. Reboot the N7. When it reboots, Stickmount shows that the sd card has been mounted. From ESFile Explorer, I can go to storage and see the card plus access it's content. I can unmount and remount the card, but if I unmount the device and remove the OTG and/or card, I have to reboot before it can be remounted. You can see in the pic which reader and which card I'm using. If it works without Stickmount, I'll report so. Otherwise, assume Stickmount is required.