I've never found the RNG to be anything but as advertised in this game. I've managed to gather HQ materials 4 times in a row when the odds were 15% and I've managed to gather NQ 5 times in a row when the odds were 45%. I've not really had similar experiences with crafting because it's been so rare that I don't hit 100% when it's something important. I've hit NQ at over 90% quality a couple times (mass producing twinthread or something), but I've also HQd things as low as 7% once or twice (obviously it was something I didn't care about since I completed the craft at 7% -- purely the material contribution). It all seems to level out to me.