graphics cards wont overheat unless they're full of dust, malfunciontioning, small computer case and case with bad airflow.
games wont make your system overheat unless your cooling is insuficient.
i get the same shit, its probably related to the anti cheat crap they put in since the client basically reloads itself every X minutes. for me it takes a lot longer tho, 50+min or so.
run L2 in a window, ull see its only l2 that freezes up and reloads.
ps: only 196.21 drivers had major issues with fan profiles which could lead (or not) to overheating cards, every other driver release since that one works fine. if ur driver is restarting ur problem is somewhere else.
In my case the PC is freezing, not just client.