Same here, got 1 from Kogan, arrives yesterday, it gets warm but not charging at all. But it is alarmingly high, just warm. What concerns me is the not charging problem. Sometimes when I put it on, the charger light lit up but the phone is not responding, then sometimes the phone beeps and turns into daydream as it is charging but after a long time the battery level stay the same.
However, there is this one occasion this morning when I wake up and see that it stay at 50%, I put it back and about 35minutes, it increases to 65%, but that is the only time it actually charges, all other time it is just stay there, not going down or up.
I am on stock, unroot and with official bumper on( the one from Google Play, not that fake one from Kogan).
-------------UPDATE---------------
So, after review the user manual of N4 and assume that the induction coil of the Kogan Qi Charger is right underneath the "Qi" logo, I found the sweet spot. As long as you place your phone's induction area (the area between the Nexus Logo and LG Logo) over the "Qi" logo on the charger (charging mat if you will), you will be fine. So this will result in your phone slightly off centre a bit, vertically.
I just completed the first full charge just now, from 26% to 100%. About 2 hours or so, fairly close to the speed you plug in the USB cord.
Most importantly, this time the phone only got slightly warmer than unplugged(from the induction area), according to BatteryLife v1.3.3, it's about 35-36 Celsius during charging and now drops back to 30.7-8 Celcius, Room temperature is above 20 or so I think? Before hand when the phone was place on dead centre, the phone temp are much higher.