I find it interesting that with a RPi 3B using a single and with the core clock down to 250MHz and the ARM at 700MHz (yes the same speeds as a BCM2835 Pi on a BCM2837 Pi) the tempurature reports 56C, that is with a room temp of 26C. And that is running RISC OS using only one core, and making very minimal use of the GPU.
I know that the BCM2837 runs a little hotter than the BCM2835, though that much. I never see the BCM2835 based RPi B+ report more than 40C, usually around 38C.
It seems that the energy density may be a little to high on the BCM2837, though that may just be my view. When I first started using the RPi 3B I did not give it to much thought as I was overclocking it and running Linux and banging all 4 ARM cores pretty well a lot of the time. Though now that I am consistantly running RISC OS with the clock speeds turned down a good bit, it is a bit concerning that it is possible for it to get that warm.