To make the mining skill worth you would should make lvling have more of an effect such as lvl up increases the speed you mine(by very small increments) or increases the damage of your pick every couple lvls. Also dont know if this 1 would be to much but you could make it were theres a small chance to receive 2 or 3 ores from the rock instead of just always 1.(agian haveing a higher lvl in the skill would increase the chance)