MC OUTPUT OFF means it is not sending a signal to the ESC as a safety precaution. This is normal and not related to how you power the Naza. If you can't get it to switch to ON, it'll be because either it isn't calibrated for the receiver input, isn't getting any input from the receiver, or the sensor calibrations are off. If you're powering the RX from the ESC, don't forget you'll need to connect ground AND signal wires to the naza... You should be fine to power the receiver from an ESC, but the normal way is to power it from the Naza. Assuming you have the V-SEN power unit, you'll have access to the built in 3A 5V regulator, which is more than plenty for the Naza, Receiver, and a GPS.