I don't have any recorded data, but before patch 2.1 went live I crafted over 10K HQ two star food recipes. At the time I was interested in converting my crafting AF into materia, so I didn't use the 100% HQ rotation because of obvious stat limitations when your gear is full of tier I materia for SB purposes. The skill rotation I was using gave me on average an 85% HQ rate (+/- ~% conditions permitting). I can confidently say that more often than not after completing 100 or 200 synths that the actual HQ result was within 1% of the expected result. As for materia melding, I don't even know... all I know is I have some horrible luck.