Raid for video editing has nothing to do with back ups. We dont' care about backing up media. Media can be reloaded at any point.
RAID has never been a replacement for back-ups.
RAID is all about performance and/or reliability of your disk subsystem.
Both correct. I don't care if my RAID array falls over on my desktop PC. I'll be annoyed because it's more work, but I won't have lost anything.
My file server currently protects me against 2 concurrent drive failures (soon to be expanded to 4) and as an absolute last resort if it all goes to hell, I have all my data on backup tape.
Some might say overkill for a home set up, but what else are you supposed to do with 10TB+ worth of data?