A little Harry Potter rumination: those little discrepancies

I was talking with a friend about the Harry Potter series, and expressed my wonder that he describes it as perfect. After all, there are some very basic discrepancies are repeatedly missed by fans of the series:

The Dumbledore Problem:How can it be that the greatest wizard of his age, is always so weak when witnessing wrongs?!? Just think about the following incidents: 

• Hagrid's Expulsion: Taking place many years before Harry's time in Hogwards, Hagrid is expeleld from school as the main suspect in releasing Slytherin's monster. But you can't seriously read this and not flinch at the flaws.  Didn't Dumbledore know about Aragog?
  (you must also ask the side question: even if we assume that fore some reason, following Myrtle's death, there was no possible way to avoid expelling Hagrid: how could he remain at Hogwarts, considering the heavy suspicions against him ? And how did the school enable Aragog's growing  community in the forbidden forest? Did Dumbledore actually have to wait for harry and ron to talk to aragog in book II ?!? 
• The Moody strangeness:  Is Albus Dumbledore on the autistic spectrum ? How else can you explain the man not identifying something strange about his old friend Moody for a *whole* year? It can't be that Barty Crouch jr. was such good a player, right ? Come on! how thick can you make one character to glorify another ?!

The Relative's-protective charm (arising out of Lilly's sacrifice). We all know that  death eaters are not very good at love-related magic. J.K.R has repeatedly told us that. How can it be that no death eater attempted to hurt Harry at his aunt and uncle's residence? After all, they don't understand the nature of that protective charm, do they? 

We could expect a few dazzling displays of the protective charm frustrating Death Eaters over the years, with a growing stress since Voldemort's return.... how come it didn't happen?

Think about it: do you really agree with J.K that  Voldy, who TWICE failed to understand the nature of the protection Harry's mother gave him in her death (the original killing curse bouncing off), really has a full grasp of the protective charm that is keeping the Dursley's residence safe? 

How could it be that Dolores Umbridge, following her confession to sending the dementors to Harry's residence (see! someone who is not a death eater actually tried ! (the confession is in book 5, p. 658). How come she wasn't thrown away from the ministry and still kept her position in book 7 ?

The inconsistencies of Severus Snape. J.K.R doesn't explain well what made snape call Lilly Evans a filthy little mudblood (book 5 in p. 571 of the first uk edition); she does state, in book 7, p. 675 (of the first US edition) state that after he allowed himself to "shout at her in his humiliation and his fury" he later came to Gryffindor's door, threatened to sleep outside the entire night if she does not come, and repeatedly apologize to her about it. Seeing his unwavering love, and the way it Navigates his conduct in the most important choices of his life, it seems strange that - 

1. Snape, the self-control master, lost it at his loved one, and at the most peculiar time - while she tried to defend him. took his side against others.
2. Did not repeatedly attempt to win back Lilly's affection for him. 

(and just as strange: Lilly's turning her back on him). 

The frustrating self-regulation:  Why do people use jinxes and simple charms when they can go for the Aveda Kedavra? have you ever seen duels in movies (westerns, sword fights, science fiction, fantasy) where people can try and kill and instead try to tickle you?

But it isn't only those disappointing discrepancies that make Harry Potter a wonderful series, but not a perfect one. There are also all those moments when expectations are built and then you get a disappointing explanation...

•   "remember my last" howler to Petunia in book 5 (p. 41  and p. 737 in UK 1st edition)
• The Patronus that saved Harry & company near the like.... (book 3)

Don't get me wrong. I love Harry Potter. It is a wonderful series. But it is not perfect. And it gets much less than perfect as the series moves on, to the level that book 7 us sub-standard. 

Rowling had, in my mind, two main problems writing book 7:

1. The chronology problem. All Harry Potter books must be suitable for the school year chronology. In book,  this made a very bad book, as she needed to drag things along so that they will take place at the latter half of the year (and the book)...in book 7 does j.k broke this limitation.... but to keep a seemingly related chronologyshe had to make the three - Harry, Ron and Hermione into idiots, who don't treat each and every item of  Dumbledore's inheritance as a crucial clue or guidance. 
2. The lack of a new theme, other than keeping the effort of killing all bits of Lord Voldemort. And after all, Horcruxes were main subject of book 6. Despite dealing with the prevention of Harry's death (the light-side answer to Horcruxes) the location and destruction of Horcruxes makes book 7 a repetitive of the subject that was slowly becoming tiring even at the end of book 6....

So, to sum  it up - not as perfect as you might have been thinking.... If you disagree, feel free to talk back or drop me a line... 

Addendum

btw, if anyof you have an answer for the following question, I'd be grateful: Is prof. Mcgonagall an Animagus or does she transfigure herself ? (or is it the same in J.K's eyes)