Steve Marvin, Lead System Designer of Warhammer Online have made an very interesting article about numbers and creativity. He brings up how numbers easily can get out of hand and that it's a delicate balance; you need to find a framework for it. A baseline.
He continue to "talk" about balance and how there's an army of people that make sure things look and sound right. Not to mention in the end it must be fun to play and experience!
In the end, however, it has to be fun. Everything written above makes it sound like a very dry and mechanical process, and in some ways it must be. But creativity is never “pure” in the sense that it exists wholly without underlying structure. It begins with a good idea, but to build it, you must have a system within which it can take shape. Context is everything. A beautiful home is built according to fixed and reliable principles of construction, to make sure not only that it looks good, but that it is sound and comfortable to live in. A beautiful painting uses perspective, contrast, color and definition in ways that can be described mechanically, but that come together into something that is a delight to look upon. An ability in the game, regardless of the numbers behind it, must be fun, and so requires a good idea to begin. But the system used to build it makes certain that one fun ability doesn't imbalance the game, ruining everyone else's fun.
Read the article here. What are you waiting for?