I have that same card and use a custom fan profile while OCing it and gaming.. At desktop, everything at stock/default..
Mine is almost a 45° line, where temps=%fan speed.. So, at 70°C, it runs at 70% of speed..
But, recently, due to some more OC I've achieved, modded the last part of it (from 70°C and up) to a curve more agressive. So, at 70°C, I run my fans at 80-90%.. Doing that, kept my temps in the 70ish.. More speed and voltages means more heat. More fan speeds to keep the same temps is logical..
What Thanny said must be happening to you: maybe it's not high enough in order to notice a drop in temps.. My advice: moddify your last part of the curve and see what happens.. Now, if you happen to be done what I explained (more core speed), it's obvious that the increase in fan speed won't be noticeable at all..
If you don't OC it, remember that this cards has a "boost" mode, where it will increase core speed on demand. Maybe that's something to consider too..
I don't mind about the sound because this are quiet cards, but I do worry about temps, so nothing to be held back for a better fan profile if I were you...
8320 @ 4,7 / 990FXA UD5 / 7950 @ 1100-6000 / Switch 810 / H110 p-p / 16 GB RAM / 23" 5760x1080 / SSD 64GB RAID0 / HX750 / SB Recon3D Fatal1ty Champion / z506