"I concede that there might have been some scheming going on between Dumbledore and Snape, although in part I think the theory comes from a place of Snape-worship. (Ducks.) "
Wow, that's a difficult comment to address. I find it quite difficult not to be offended by it too, which isn't very constructive of me, and I'll try not to let that colour my response.
I really don't think that I'm guilty of leaving my intellect or critical faculties at the door out of a particularly passionate attachment to, or idealisation of, the character of Snape. I think he's one of the most interesting characters in the series*, because despite being intelligent, talented and passionate about his own stuff he's also quite clearly petty, mean-spirited, emotionally immature and a spectacularly bad teacher. (Let us keep in mind that I'm a primary teacher myself, and that Snape, along with Hagrid, makes me itch to send a Wizarding Ofsted team swooping down on Hogwarts to summarily dismiss half the staff, starting with them.)
I think that JKR loves misdirection, and that she has shown that in every single book in the series. For her to include Chapter 2 if Snape IS indeed working for Voldemort is indeed pointless and flabby writing that undermines the impact of the last chapters. For her to include Hagrid's overhearing of fragments of a conversation between Dumbledore and Snape, and for the trio to leap to the assumption that this backs up their suspicions of Snape, if Snape IS indeed the villain, is clumsy and slap dash and the very opposite of what JKR has done in all the previous books. If, on the other hand, she's feeding the trio red herrings - well, that fits right in with her writing in all the previous books. I wish I had my texts to hand so I could pull out a list of citations - but this is what she does.
I also think that the message that all that is gold does not glitter is a good one, and a damned sight more interesting than 'the ugly, greasy, mean-spirited guy IS evil'. The introduction of Slughorn (and indeed JKR's words in her interviews) back up the notion that her Wizarding worldview is more complex than Slytherin=Villain.
"But, nope on the second chapter. Not saying the first chapter was strong, but as Fay said, it's in keeping with the other books."
Sorry, sorry, I expressed myself badly if you've understood me to be saying this. I think that Chapters 1 and 2 both mark a big step away from the other books. Each book so far has started out with Chapter 1 re-introducing us to Harry Potter in his miserable life in Privet Drive, generally on his miserable birthday. It's been rather comforting and Roald Dahlish. OotP, although my least favourite book in the series, definitely made moves towards taking the HP series away from the traditional children's school book setting. HBP leaps even further by having the first chapter NOT from Harry's POV, NOT introducing us to him on his birthday at Privet Drive. It pulls the rug out from under the reader's feet, confounding expectations by showing us the big picture from an outsider's perspective. Instead of another reassuring summer holiday of discontent, we see some of the chaos errupting into the Muggle world.
"The second, on the other hand, was uncharacteristically clumsy and heavy-handed misdirection, if misdirection it was."
But why do you think this is clumsy and heavy-handed? It seems that your reading experience was not "Oh, please, like I'm going to fall for that!"
*I don't know that I'd say my favourite, at least pre-HBP, because there are lots of her characters I really enjoy. Post HBP, though, he really is, on the basis that (by my understanding of the text) he's doing something really interesting and heroic, despite not being an obviously heroic character.