Mining is without a doubt the most powerful weapon skill in the game because you can train it very quickly and safely by mass mining useless dirt and rock, then because of the penetration and contact area values picks have it's like wielding an axe with the penetration of a spear, and on top of that picks have no dud attacks like pommel bashes with swords. Oh and mining trains the strengh attribute, because the digging crew weren't dangerous enough already.
I've seen drafted miners chop trolls and ogres in half at the waist, lop dragons apart and turn entire armies of goblins into chunky salsa. In general any attack by a skilled miner will take a limb or head off a normal sized enemy, which is not unusual for skilled wielders of edged weapons, but miners take you by surprise because you don't initially expect them to be so deadly and they tend to be more skilled than a conventional militia early on.
Sadly this does mean a berserk miner will kill almost every dwarf they meet. I had more than a few forts decimated in the past when madness was more common because a miner went crazy. Often they would blend the military I sent to try and put them down, and just keep blending their fellow dwarfs until one of my other miners got a lucky shot in and killed them. One went crazy in my meeting area once and the entire place turned red in about three seconds as limbs, teeth and heads flew through the air.