I think that the last class will have a energy system that relies on balance. I originally had this idea for the Wizard's instability but with that gone, I think they could apply it to the last class. Overall, how it works is that half of your skills drain one side but raise the other. The other half raises the opposite side and drains the other.
For example (disregard names and skills, this is just to illustrate how the system works and not what the last class will have):
Mulit-shot: -15 concentration +15 nature
You loose concentration since it is needed to shoot the arrow but you gain nature from not using it.
Venom: +10 concentration -10 nature
You loose nature since you need it for the spell but regain concentration because it was not needed for venom.
Now, to make sure that you do not have an unlimited supply of energy which none of the other classes have, there will be an imbalance to some of the subtraction and gain like you +15 concentration and - 20 nature for one spell and -30 concentration +5 nature for another.
What this system allows is for a wide use of differing skills but you cannot constantly spam one skill over and over. But does allow for continual use of different skills. Strategy is also needed for this system to maximize the amount of spells you can cast without running out of energy. Blizzard has said that they want these different systems to help drive how you play your character and this does just that. It is also fairly simple, which is also important so players don't have to think too much about their energy system. When out of combat both your concentration and nature will regain since you are not using either.
This system can also be applied to a number of different situations the last class may have. If it is a bow user, the other side can add a bit of magic for him to use. If he has a pet then one side can be for his attacks and the other for the pet's. If it is for some sort of knight class/tank class, one can be for defense and the other offense. The point is, the simple mechanic can be applied to several different situations and still be viable.
Edited by NorthAmericanPenguin, 31 August 2010 - 11:09 PM.