I would like to throw my two cents in, overall the RNG is functional, but I would say it is broken to the point you have to adjust any percentage you see. I think everyone who has done a lot of crafting or gathering (or followed a lot of loot drops) knows, there are highly unlikely occurrences both directions, and "unlikely" strings of failures and success are common, when they should be statistically rare. Overall they tend to average down to a baseline, but that baseline is not the listed number in my experience.

Ignoring failures, look just at HQ for the moment. When I first started playing with using Unearth I did some tests to see how well it worked, and if it was worth the waiting for GP every few nodes, or paying for cordials.

Copper Ore @100% chance, 15% HQ. Using Unearth at every single node, so 25%, and 30% for +5% nodes.

I mined a total of 75 nodes(I was going to do 100 but I can only take mining for so long....) , so ~300 total ores mined. At the end I had 38 HQ.

That is obviously not 25%, more like 12%. While I haven't done another test to further verify this or do an even larger sample, this upholds my experience with RNG in this game: subtract ~10% to get the real world average percentage.