rMBP burns my fingers when gaming/using the 750m.

76° to 78° C is more than within parameters when it comes to CPU temperatures.

Maybe use an external keyboard if you do not want to get your fingers burned, though even with 100° C on my 2009 MBP it never happened to me. It was hot, but no burns occurred, thus if you have burns from touching the metal, maybe measure the temperature with an external thermometer?

Those Macs in their heat - a sine of over-heating? - a short story by Mister GGJstudios

I have spent some time playing games on my 2012 rMBP, often holding the laptop on my knees, and while it surely gets warm, it would never got HOT to actually burn me. The 78 °C is the temperature on the sensor, which is within the CPU/GPU core (depending which one you read). The top of your keyboard is much cooler. It would be of course interesting to record the actual temperatures... When holding the laptop on my lap, I estimate the max temperature of the bottom casing to be around 45-46 °C, which is definitely enough to give you 2nd degree burns after few hours of exposure. But I'd say that anyone who keeps the laptop there for so long kind of deserve the burns

You have some incredibly sensitive fingers if they burn from the heat radiating from that top strip. I see my machine run a decent amount higher than that and I've never had my fingers burned.

Now, I touched the back of my desktop's GTX 780 once, that was a whole different mistake.