Here's a solution which I read from a Apple forum:
to reduce the 'other' space I:
- performed a complete Backup (from iOS Device context menu)
- performed a Restore (clicked Restore button on Summary tab)
- after device is reset with latest iOS software, chose latest backup
However, if you choose "Restore from backup" from the Device's context menu, you WILL introduce the corrupted 'other' from the backup, as you said.
Another solution which I found by myself without using the "Restore" method:
- Close all apps
- Reboot or Hard Reset (press home and power button)
This will clear the unnecessary "Other". Now I have freed about 33GB of unnecessary "Other" space.