Hello... Well you ran a stress test on a lower tier GPU... it IS going to be Harder and take longer on it than a upper tier model... I recommend not doing many stress tests on it... as you can see what it will do to your hardware... Lower 80's should be a Normal/typical operational MAX here for a 700 series Nvidia GPU B /
My only other test suggestion would be removing a cover from your CASE, and seeing if the Normal High temps is a problem with available Cool air or exhaustible Hot air from your case.