I've never thought go it that way but this makes a lot of sense. Or it could be that all Cerberi don't necessarily have a weakness and Fluffy in particular is vulnerable to music.

 

Maybe he was trained to fall asleep like that, for safety reasons? Fluffy was a perfect deterrent against casual peekers, the rest was basically a walk through. But the Mirror protection was the real kicker. I don't think Voldemort was ever going to get it by himself, and from what I understand Dumbledore nearly showed up in time to duel Quirrelmort himself.

CoS, well frankly, Dumbledore isn't omniscient, and while he may have known the creature was a basilisk, or easily deduced it, there still remains the problem of finding the Chamber itself. And honestly, thinking that it was in Myrtle's bathroom was a truly massive leap of logic that people of Dumbeldore's age and wisdom have learned not to trust in.

PoA, nobody new Sirius was an animagus save two other living beings. Not to mention Sirius had a way or two into the school. And after the near attack on Ron, I'd wager that Dumbledore grew very curious and increasingly suspicious that something else was amiss. Afterall, Harry Potter would have snuffed it, right then and there, had Sirius wanted to kill him. So would have Ron. And yet, both survive, relatively unharmed, and there isn't even a hostage situation to boot. The first incident when the Fat Lady got mauled would have alarmed him greatly but the second one? Well fuck it, clearly Sirius is just that damned good, and likely not just as his animagus but likely with an Disillusionment charm or two as well, and clearly he could have killed Harry. But he didn't.

So yeah, the first three books, kind of have big holes in them, but not that big. Dumbledore isn't perfect, powerful and intelligent, but not perfect. Same with Voldemort really.

 

In my opinion the worst example of poor planning by Dumbledore is the assisted suicide in the end of HBP. He goes as far as getting himself killed to create a perfect cover for his spy, and tells no one of this plan. Harry and co. I can understand as they are kids and their mission is by necessity a covert one and they don't really need to know, but the remaining leaders of the Order could definitely have used any information Snape could have got them to help the people. Say, stop Voldemort from completely annihilating the ministry and the aurors while the good guys were partying...

Obviously it needed to be so or the dramatic reveal in the end of DH would have been less dramatic, but it's still an example of Dumbledore acting as a plot device, not as an independent, rational actor.

 

Its always been my theory that Dumbledore's main goal in life was to set up as many dramatic reveals as possible. We see this at the end of book one, in your example, and basically every time he shows up. He just really loves dramatic reveals.

 

How is this poor planning? Are you stupid or something? Creating a perfect cover for a spy....means you want as few people as possible to know.

So. Um. That's not a flaw. That's a desired feature, not a bug. That's competence.

 

A spy is not a spy and as such totally useless without a handler.

Not to mention that Dumbledore's endgame relied heavily on Snape delivering a crucial piece of information to Harry; yet he set things up so that Harry was most likely to try and kill Snape on sight, and unlikely to believe anything he said. The "Snape gives his memories to Harry on his dying moment and Harry takes them on face value" plot device was absurdly unlikely to happen as a part of any plan.

 

Yea, a spy is useless if they can't pass on the information they have. It was a pretty ridiculous batman gambit.