First thing i'd suggests id test w/o the OC'n it does it still run hot? Also compare the temps to the operating temps in the user manual if it's outside these you may have a issue playing for extended or even short periods, if you're using a destop pc you could also see if you can re-arrange your PCI cards so your GPU gets the best possible airflow, and clean any dust form the fans, i do this every few months.

i have notice compared to other games of the same quality of graphics, FFXIV hammers my ATI card but the temps are always within operating temps so it doesn't bother me too much.