I’ve been playing him in my own worlds for a while. A fully levelled up miner can easily do the job of 5 hearthlings when it comes to mining; increase that to 10 if you manage to get him the highest level pickaxe. He is very powerful for digging, but I don’t necessarily think he’s overpowered. It takes him quite a long time to level up, and because his promotion talisman is crafted by the blacksmith, in most games it will take you a while to even get to the point where you can train him. I intended him as an advanced class all along, the thinking being that until you get to a large, developed town, the regular workers are more than enough to fulfill all your mining needs. It is once you’ve essentially done everything you can with regular workers, once you’ve set up all your crafting chains and have a large enough population to support a massive inventory that the Miner produces, is when you should really be using him.
In retrospect, the Miner has two main purposes: one is fast mining, but the other, and arguably more important one, is freeing up worker hearthlings to do things like building, or picking up after the miner, so your mine is clean and usable a lot faster than with regular workers. I’m finding it a lot easier to focus my workers on things when I have a dedicated mining class. All we need now is a dedicated hauling class OR dedicated builder class, and I think lategame will become a lot easier and more fun to develop.
I hope you enjoy the mod when the optimizations roll about, thanks for looking.