With mining being as overcrowded as it is, the way bonus chunks are currently set up makes it more beneficial for a player to NOT level mining than it is to level mining. Since rocks are becoming fewer and far between, the longer you can mine on any rock = the more helpers you can get = bigger benefit. I am already wishing for the "Unlearn" skill so I can put my mining back down to a lower level.
It's kind of confusing in my mind why it was changed in a way that would benefit a lower level miner in the first place. While I do enjoy all the bonus chunks that I've gotten, I think it's important to make mining worthwhile to learn. With diminishing returns on gems, and less bonus chunks with higher level mining, it is kind of pointless to learn the full skill tree.
I mean, I could get upset that someone with Botany skill has the option to poison trees and I don't, but it shouldn't be changed to where no matter the skill level anyone can kill trees, just like I don't think mining should be more beneficial to lower levels.