I am running the same 3600 with the wraith stealth cooler, I have exactly the same readings. I also get the fan 'heartbeat' being caused by a 10 degree spike in temp every 3 - 6 seconds. After doing some extensive reading this would seem to be all normal. Also, ironically the AMD Master software causes a bit of CPU load which will increase the idle temp so this would not be a true idle temp. Some setting adjustments fixed the fan pulsing and the CPU seems happy at these temps.
Interesting forum here regarding AMD Master.