I forgot the tips for improvement, sorry.
1. Get a beta.
2. Write longer chapters.
3. Don't use OCs unless you have a good reason to use them.
4. Be more realistic with your romantic entanglements.
5. Think of a plot-line that hasn't been over-used and go with it.
6. Avoid Severitus and Draco-love, they aren't particularly well-liked in this archive.
If you want to continue writing at your current level, do so by all means. However, switch to the MC or other band archives they have on this site, or go to FF.net. Both are much less strict and much more....friendly than the HP archive on Ficwad.
Author's response
I seriously don't care. I write what I love. If you people don't like it oh well. I'm over the negative ratings. So what. Big deal even the best authors had to have a bad story or two. My grammar isn't perfect but (usually) my spelling is and (I think) spelling is more important then grammar.
I personally wouldn't waste my time my time writing a band fic. Why? Because, I don't care about them.