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@Psyko, I figured out the ideal solution. This was annoying me as well, so I thought I'd register and share!

Simplest hack is to move all files you want excluded to a File Sharing folder (like VLC). If you really want to keep that 740MB VLC data backed up, though, use another app like Chrome. These file sharing folders are located in On My iPhone.

If the folder is not there, copy at least one file into File Sharing (with iTunes on Mac or PC), then the folder will be created in On My iPhone on your device. Stash the files in that folder, then exclude the app from your next backup.

Below is my screenshot showing VLC excluded. Hope this helps!
Thank you, Thank you, Thank you, I wasted a lot of time trying to find this solution.
 
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