Been battling this issue on my phone (32GB Nexus 5) for the last couple/few weeks now. My dad's phone (16GB Nexus 5) has had the issue much longer, I guess since 4.4.4 as I don't remember either phone having this issue prior to 4.4.4.
My dad's phone is basically stock - no extra camera apps, no Skype, etc. Pus he doesn't use the camera.
Strange thing is both phones only seem to have the issue after pulling them off their charger (Google or TYLT wireless or the factory wall charger) at which point mm-qcamera-daemon almost immediately pops up in the Battery stats and starts rapidly draining the battery. If the phone is restarted as soon as it is pulled of the charger (or if it is charged while off and turned on while off the charger) mm-qcamera-daemon seems to stay away.
This is whats happens when I try to use the camera (stock camera app) once mm-qcamera-daemon appears under battery stats:
Anyone know if Google is still working on this issue or if they even care? Hopefully next major Android release fixes this?