I am the Kat that Walks By Itself

Grey is fine. Dumbledore's a very flawed character in canon, for a mixture of reasons including both elements of the early style that may not have been meant to be taken very seriously but are still there, and definitely serious developments later in the plotline. Likewise, Snape is interesting, and there's a lot of fic sympathetic to him that I've enjoyed.

But your description of this one sounds pretty much like tearing down one character for the sake of another, which is usually not much fun even when I like the characters the author is favoring.