I confidently predicted that Dumbledore would be killed at the beginning of book 7, and I can't explain why the end of book 6 feels so much earlier to me! Well, no, wait, maybe I can -- the beginning of book 7 would have felt like Dumbledore's death was the start of the climax of the series, maybe even the catalyst for events to start moving faster and faster; the end of book 6 felt to me like his death was isolated from the events of the climax. Maybe it will feel different to future readers who don't have a long wait between one book and the next.

Of course you're right about the mentor death, though; I'm surprised Molly and Arthur Weasley have made it this far.