[DustyPorViva]

Well it wouldn't be nearly as complicated or timer-sensitive as DDR :P
But really just adopt the 'press the button they tell you to' thing. Then again... that would be more annoying than pressing D over and over because now you have to actually focus on mundane repetitive tasks.
I say stick with what it is, after thinking it over. Stuff like mining will never be fun. Not because they can't be, but because people will be doing it so much they will want something as simple as can be, so they can do it a lot without having to really focus. I think the best thing to do is keep with what I said, make it fast paced.
If you make rocks break in 5 hits, and have a sprite for each stage of the rock being broken, so that there is visual confirmation of their progress, and knock down the price so that it fits with how much rocks they will be mining, it will be faster, but won't be as dull.