The answer could be simple to getting things back to normal. If you have had your GPU in your case for a while...you may have a bad case of Dust Bunnies. I was overheating in STO and was wondering why...I then had a light bulb moment.
I live in a house and there is dust, and unless you live in a clean room, you probably have it to. The fins on your GPU's cooling may be clogged or covered with this wonderful insulator. I was running with zero load 72 degrees C with dust. After a good vacuuming, I am down to 62 Degrees C. Still not good, but that is why they sell cans of air.
(Evangelist Voice) So my brothers and sisters, if you are burning up in the fires of the game. Look to your case and open the way. For inside, your poor hardware sits. This sinister agent of the devil may be waiting, and this fix is the easiest! (/Evangelist Voice)
For those that this is is to obvious...it is. Even new cards could be victims cause it only takes four months to get a nice blockage going. These have been my two cents.
Preventative maintenance is always a good tip. I recommend blowing out your computer case every 6 months, and more often if you live with a lot of pets. I good bottle of compressed air can save one a lot of hassle and expenses in the future.
Yeah, I resurrected my old computer from the dead a dozen times by simply opening it up and cleaning it out properly. After 8 years I gave up on it dying completely and got a new comp, lol. xD
Same story with my oldest TV that turns 20 years old this year (as old as my lover actually, tut...). Electronics can last an incredible long time if taken care of properly (and with a little stubbornness and know-how at times; is no secret I'm a true Taurus in regards to being affectionate about my stuff). :3
It may seem silly, but it's incredible how such small details can make such a big impact, but they do. Sensitive stuff.