Definitely using an offset over a manual/fixed voltage. I used the OC tuner mainly to give me a baseline result, and I figured I could take over from there....took a lot of the guesswork out of it. The last time I had it at 4.4GHz it was running at about 1.300 volts, and I offset it to ~ 1.256v, temps were great. At those settings @ idle it runs at about 1.080v if I remember correctly, which is great.
I know what you mean about OC'ing from the Asus AI Suite, it's decent for basic oc'ing but not much past that.....I didn't even bother installing it this time.