It's not too uncommon. It's been happening for decades. I think that it is appropriate to treat it as a warranty issue.

Usually a MOSFET, Capacitor, or Inductor burns up. It just happens. Heat takes its toll or some latent defect surfaces, the compoment fails, shorts out, and 100+ amps is available at that location to make a quick impressive display.
Here is an explanation of a common cause:
https://forums.evga.com/V...-on-fire-m2729642.aspx

fearpoint
That's pretty unacceptable.
 
Warranty or not your products should not be catching fire with regular use unless you sell firewood.

If a product operates for it's original intended warranty specification (in this case 3 years) and then fails outside of that originally guaranteed time how is that unacceptable? Components degrade over time, that's just a fact of life nothing lasts forever. It's not like there is some pandemic of 900 series cards all failing. You may think so because of this microcosm of a forum that you read posts about it every now and then, but the reality of the matter is that there isn't some major defect that's wrong with them. Consider that the 970 in particular was at one point the highest selling video card on the market and has literally millions upon millions of units moved. People don't post just to say "hey, everything is still fine with my video card".