I don't know... It seems... rushed. The intro part is missing, so it starts rather suddenly, and this version lacks the power of the original. Especially the part from 00:22 - 00:26 seems too fast and weak. Some big drums behind the big notes would sound good, and help give some oomph to it. Also the brass doesn't hold notes for very long, and it doesn't sound as good. Maybe I'm just comparing it to the "official" orchestral boss battle version, which included a segment featuring this song, which I loved. It seems like it would be a good launching point if you wanted to improve it, though.