As the others have said, auto over compensates the voltage so use manual. Auto doesn't tweak the cache either.
I found that the Hero really adds too much voltage. I had a play when i installed mine and found that for the cpu level up at 4.4Ghz it applied 1.29v vcore when it only needs 1.264v manually. Less voltage, less temps!! Never has it been so important as it is with Haswell.