Is the case closed or open? Mining is harder on the card than gaming; mining is designed to use it 100% all of the time. Gaming doesn't do that.

I have a 270X rather than a 280X, but even in an office with temperatures in the low 60s F and an open case, it still runs the fans at 4300 RPM (~84%) to stay below 75 C.

Set the fan to 85% and see how loud it is and what temperature it runs at. If it stabilizes below 80 C, it's ok. If it's too loud for you, then it's too loud for you and you won't be mining. In cgminer that's [G] [C] [F] [8] [5] [enter].