Hey guys, I got this same overheating issue with two TYLT chargers and two different Nexus 5's. I have read about a short term solution that so far seems to work.
Cause of overheating:
1. When the phone is placed against the charger, but 3/4" or so above the chargers bottom plate and then slide down- this can activate the top charging coil.
2. The phone is then slide down the charger until it contacts the bottom plate. The keeps the top coil active and begins heating the metal (magnetic) circles in the back of the phone.
1. Place the bottom of the phone directly onto the bottom of the charger without sliding it down the charger stand. You can do this by angling the top of the phone away from the charger, kinda of like butt first approach. This will keep the top coil from activating and all is well.
Best of luck