pawelblyskal
If you decide to overclock at 112% power limit this card will fry without having to run the fan at significantly higher than normal speeds. You have shown 94c at the BACK of the card. This means the actual VRM unit on the front is running well over 105c if not more. You also show exactly the point where the cards are catching fire. It pretty clear the VRM at this section of the card it reaching thermal run away. This is exactly why you need the additional backplate to dissipate the heat via thermal pad.
Well EVGA has already stated the VRM's are rated at 127C and I don't think they're getting anywhere near that, at least on my card. As far as the thermal pads are concerned, I'm willing to bet the one that goes over the VRM's on the front directly in contact with the cooler will have a bigger impact than you adding a backplate with a pad on the back of the PCB.
In any case, they'll send them to you for free. Start with those pads and if you're not happy, buy a backplate.