I understand that the class are under heavy tweaking ATM but I think we should ask the community for some ideas. Also if I may suggest I have an idea for the whole mining thing:
Players will have to start with a wooden pickaxe. They will need to use it long enough to where they will then level up their pick axe skill and they can then use the stone pickaxe and so on all way up to diamond. Every class will be able to use diamonds, The bonus that the dwarfs will receive is that they start off on the stone pickaxe instead of the wooden pickaxe. If we wanted to we could also do the same for axes and shovels and swords. Swords would be a little more skeptical. You would unlock the next higher tiered should just like a pickaxe but you could only use the ones specified by your class, instead of being able to go all the way up to diamond or iron.
I also if I may suggest I think that some of the exp rewards should be changed a little bit:
Gold: Should give 8 exp instead of 6
Obsidian: Should give 30-45 exp instead of 15
Sand: if gravels going to give 2 exp then sand should give 2 exp instead of 1
Crops (planted by you): Should maybe give you exp, that way you could earn exp through farming.
Redstone: Should give 14 exp instead of 10
Those are all just my suggestions to help balance things a little bit.
Thats all I have for now post any comments on good ideas for races/classes/mining/ect.