It isn't necessary to think of "God" as a creator. But if you do, then the evidence for it is simply: everything. ;-) "Everything" is so big that people can't even look at it or grasp it. That's why they prefer to fight about little things instead.

What if the key to astrology (like tea leaf or palm reading) is NOT the technical rules of astrology itself, but the perceptiveness of the reader? What if the reader has some natural divining ability, and the method is just a frame to hang it on?

Having known people who were uncanny at reading tea leaves and seeing future probabilities thereby, I suspect that the "method" used in divination simply doesn't matter, and it is not the determining factor. The method is just the instrument you arbitrarily pick on which to play the song you want to play, to use an analogy. The instrument doesn't make the music...the player does. Any instrument will do.

Any divining method will do, if the person doing it has the right talents and feel for it. They will pick a method that they like. It might be astrology. It might be tea leaf reading. It might be a crystal ball. It might be anything. It doesn't matter. You will not be able to prove anything by analyzing the method, because the method isn't what makes it work. The reader makes it work, if they have the native ability to do such readings. And that cannot be proven or disproven, it can only be demonstrated in a way that will convince some, but not others, depending on their preconceived notions and inclinations.