I am the Kat that Walks By Itself

I do not believe there was anything odd about Dumbledore's characterization. If anything, his portrayal has turned out to be one of Rowling's triumphs.

I suspect that deep down, Dumbledore, like most, was a complex personality with both positive and negative traits. I think Rowling allowed readers to see the "best" of Dumbledore in the first six books, since the stories are basically from Harry's POV. And in the seventh book, she reveals the more unpleasant side of Dumbledore's nature in order to show how Harry developed a more mature outlook on the former headmaster. This revelation allowed Harry to begin to understand that people are a lot more complex than he had always believed. It's called "growing up".