If your GPU is under max load it will reach it's hottest temp possible, regardless of what application is stressing it. If your temps are out of the ordinary it may be time for a repaste or a change of chassis that allows better airflow. You can also try aim for a lower FPS target to take some of the load off if you are comfortable with that.

That said, this game is the most GPU demanding game in my library and that is hopefully because they haven't touched optimisation yet.