'Other' also includes things like Safari's cache and cookies, notes from the Notes app, Calendar events, Contacts, Mail messages, ebooks from Kindle/Nook etc, and content from other apps e.g. newspaper and magzines, PDFs etc. But yours does seem larger than it should be, unless for example you've got other videos in AVplayerHD - if so have you tried deleting them to see if 'other' goes down ?
If you havn't got other videso in that app, then as far as I know the only way to remove/reduce the size of Other is to restore the iPad. You could try restoring to your last backup first (iPad backups and restoring), and if that doesn't reduce Other you will probably need to restore back to factory defaults and then add your content back onto the iPad.