Those were eminently reasonable expectations based on what we had seen in the first six books. That they were not fulfilled does point to an artistic failure on Rowling's part.

Those were your expectations. That doesn't mean that it was an artistic failure on Rowling's part. The plot wasn't meant to go in that direction and that's why she didn't write it.

It's fine to love the character for whatever reasons you want, but you can't blame her for not writing him or the plot the way you wanted. It wasn't her failing because it went a different way. That was my point.