I think you have to be pretty egotistical to say the character you have described as the cleverest witch of her generation is a self insert.
The characterisations in Harry Potter aren't bad. Luna's character is consistant and enjoyable, Ron's is also pretty consistant, as is Hermione, Dumbledore, Snape and Voldemort. With the shit going on in Harry's life it's no wonder he's all over the place.The rest don't really matter.
Ginny is the only main character with poor development if you ask me. After being posessed by Voldemort in her first year and thoroughly exploited, I can't understand how she transformed into the character she was when she was reintroduced in book 4, just two years later. Her character, fears, and motivations weren't really explored.