A few thoughts...
First, unless you're holding onto a particular old app version that's been made unavailable, you can always simply re-download apps from the iTunes store. So there's not (typically) much point in worrying about protecting them from data loss.
Second, a Raid1 NAS is a great device BUT it's no panacea against data loss. You've simply eliminated loss due to a hard drive dying. Still lots of ways to lose your data: A bad network write, accidental deletion, theft or destruction of NAS are the first few that come to mind.
Better to leave the files on the computer where everything expects them to be and have the computer files backed up to the NAS automatically. TimeMachine on OSX works great. Altaro Oops!Backup provides similar functionality on Windows.
Ideally you should then periodically backup the critical files from the NAS to a portable drive and store that drive offsite.
