What you need is a file browsing program like iExplorer that let's you see the files inside you iPhone or iPad. I had 7GB of "other" on my iPad. When I went into the media directories on my iPad I had discovered about 6 GB of movie files that should not have been there (I had no movies on the iPad). I deleted those and now have just over 1GB of other. I'm thinking they were left over temp files from streaming iCloud movies. Anyhow scored me some precious extra space.