That sounds like a high temp for those volts. Make sure your cooler is a) clamped with well...I believe it came with a backing plate so it should be good, and b) that you have enough but not too much thermal grease. These are both areas I've had problems with in the past, the first though with the Intel pins.
This is a good but not great OC heatsink. Frosty Tech
had it 7-8C warmer than a Xigmatek 1283 or TRUE.
You may find you can run lower voltage at that speed, however, your voltage isn't that high. I went to an inexpensive water solution (Swiftech H20 220 Compact) with slight modifications (clear tubing, 38mm Panaflo fans in pull, and 1" shroud) and never see over 50C...even with 1.55v in BIOS and 3.6GHz (although I haven't found the combination to be stable at that speed).
Arctic Silver 5 is the long standing benchmark for thermal grease. Their Ceramique is only a little behind and has low conductivity. Arctic Cooling MX-2 tests in the same range and like Ceramique is non-conductive. Coollabortories Liquid Pro is supposed to be measurably better but apparently a pain to work with...and highly conductive, very difficult to remove, and needs to 'melt'.