Do you have a good mount? I would check that and make sure first as that can be a huge issue, but you should be aware that there is a delta between the IHS and the evap head, so expect a variance, though yours does sound a bit high.
I would remount and then check temps again, my single stage was able to keep my 3960X cool at 5.4 through PCMark 7 with no issue, but Vantage would not run at those clocks.