This may apply to other collecting as well, not sure... but I noticed it this weekend with my Earth Genasi, Loremaster/Gatherer using God's own mining pick axe. I have definitely noticed a drop/cap in the yields of, at minimum, coal.
Instead of getting an average of 11 chunks, I am now getting 9 every time, without variance or fail. I've seen other characters getting the same yields consistently, when they're neither an earth genasi, a bard, nor a loremaster with gift of gathering.
I would love some transparency into the change, why it was done and how being a dedicated miner is in any way better than a casual. For right now, it feels like I've been screwed out of a Greater Award. Perhaps this was unintentional, maybe this is a bug?