You are right, this kind of manip!dumbles fic is very common, but this is one of the best I have read.
The characters are believable and their responses logical. The story is thought provoking and emotionally engaging. Plus this fits the tone of the last few few books making it a believable AU. I think JKR wrote the personality's of her characters so many of these events are not only possible, but could be likely in some cases.
damn good! (two thumbs up)