This is quite good. I can see how your wife beta might think of it as a feel good as there is a certain satisfaction in seeing "the bad guys" get theres. But the scene with Luna seems out of sync with the rest. The comment 'He was alive again, but all grown-up' creates, certainly unintentionally, a notion of Harry returning in some way. I thought for a moment you might be leaving the door open for a different sort of Harry returns to (younger) life story.
Also, why would Harry's death lead to Dudley becoming magical? While it makes sense to sense Dudley raised differently and so becoming a decent person, it wouldn't naturally follow that he would become magical.
OK, Lets deal with these one at a time. It's my sister who is my beta. (I'm a widowed dad.) She hates any type of stories where justice is served. She also hates my dark(er) Harry stories (unfortunately not yet posted).
Luna does tend to be out of sync with most of the world. However, I tried to make her visions appear to her in a manner that a four year old could accept. Technically, neither she, nor Hermione should be involved at all, because they never met Harry until school, but as they are such an important part of the overall story, I added them.
The reason I added Dudley is because he needed something. Yes, he abused Harry too, but at five, he really wasn't responsible for his decisions. Daddy said it was OK, and so it was.
Harry's death was not the cause for Dudley's magic, but it may well have been the catalyst. Additionally, Magic seems to run in families. Lily and Harry were magical, and Petunia was at least aware of the magical word, though she couldn't enjoy the benefits, which accounts for her jealousy. If she had a latent talent, she could have passed that on to Dudley.
Vernon's abject refusal to accept anything but what he considered normal, could easily have caused Dudley to instinctively hide any magical outbursts, or blame them on Harry.
I hope I've answered your questions, and thank you for your well-thought-out review. Alorkin