You should raise the fan if you feel its being too hot.
Too much heating can blow up your card, and if not it shortens its life time drastically. Just make sure its really being very hot.
And remember, comparing video cards to CPUs is like apples to oranges.
In CPUs the danger zone is said to be 75+ but in Video Cards, it is perfectly normal for about 100. Some gamers even reach 105 without any problems because its meant to be heated so it is also able to withstand high temperatures.
You can always set your fan to a 100% if you still feel anything like that but all in all, I won't suggest tweaking fan speeds if it is below danger zone. The best option however is water cooling.