They should really replace the digging system with a sub-window. This sub-window would contain a progress bar and a rock face. You click on the rock to whack your pick axe at the target area. If you *hit* you gain 20% mining progress, and it resets(to random) the location of the part you must hit. If you miss your pick loses a little bit of durability/sharpness.
Your mining skill would
slightly increase the circle area in which you must hit(perhaps by 1 pixel), and would increase the amount of progress gained per hit(again, by 1%). The progress could also go up slowly, like by 1% per second.
Once it reaches 100, you successfully mined something. Yay, fun!

To further complicate it, there could be a cooldown time on whacking the rock - say (2.5 seconds - (Strength/100) seconds) This would make a weak mage able to whack the rock every 2 seconds, but a strong Kran able to every 1.25 seconds.
Then they could also change the hit-area sizes and the progress gained depending on the mineral being mined. Iron could be 30%, Gold 20%, Crystals 10%, \"Rarest-Metal\" -10%(meaning you\'d require 11 mining skill to even get 1% per hit. Ofcourse, if you gained 1% progress every second, you wouldn\'t need to hit, so it would have to be something like (progress you hit for)/60 per second.
Or I suppose they could even reset the progress bar every time you miss - that would be evil though, and would depend entirely on luck.

Just some thoughts.