The Occlumency subplot of this book seems a little wonky to me. Was Snape really the ONLY person who could teach it to Harry? Especially considering how bad of a teacher he seems to be!
Considering that the main thread of the book involves a group of students learning magic beyond their years and teaching it to themselves, why would that not have been an option? As precocious as Hermione is at basically everything except flying, I find it not improbable that she could learn at least passing legilimency to practice it with Harry.
Also, the entire premise of the training seems to be misguided. I’m not sure how effectively practicing intentional, proactive occlumency against overt legilimency would translate to passive occlumency (while sleeping!) against a remote threat.
Also, does it seem odd to anyone else that the centaurs would be so possessive of the Dark Forest? After all, they are part horse, so I would think they would prefer open plains for galloping around. And they spend so much time gazing up at the stars that I would think they would prefer a dwelling with a less obstructed view of the sky!