The probabilities do seem a bit off when you consider a large number of items being made. I just gathered up a bunch of copper and tin ore this morning before work. I then made as many HQ bronze bars as I could (50 bars total). All the 100% attempts resulted in HQ bars. Out of all the bars I only got to 71% (about 20) , I only made one HQ. I got about 5 to only 18%, and one of them became HQ. It seems the percentages are off in the middle of the scale.