sometime the core temp sensors (i think some one called it stuck sensors) can just report it wrong i had a q8200 that when overclock to 3ghz was 65 on the cores and 58 by the mobo temp but i left it unused for 3+ months and when i came back to it, it was reporting it at 85-95c but still on the mobo cpu sensors it was stll at tell me it was t 58c
I have just finished overclocking my i7 950 to 4.2GHZ and after running Prime95 for 1.5 hours at an ambient temperature of 22 deg c, my cores peak temperatures were 74, 72, 72, 69 using Real Temp.
Voltages - vCore 1.31v - DRAM 1.60v - QPI 1.35v - CPU PLL 1.80v
My case does have a lot more cooling than yours and that may be a contributing factor. I have attached some pictures (not as clear/good as yours) but they might give you some food for thought.
I am not sure what else I can add over the other comments but before I bought the NH-D14, I researched for 4 weeks and this is by far the best air cooler on the market from the reputable information I found.
If you tested it outside the case with no difference in temps, the case isn’t the problem. After treading a few posts on the web I can only say it DEFINITIVE the motherboard(after all you have already tried). Supposedly it has jumpers which can set for variet overclocks. The best thing to do is to reset the to default(it appears you mobo is giving the cpu some extra juice which isn’t needed)