I have a not dissimilar strategy to some of you guys.
My main documents are on Dropbox, which is mirrored across a number of computers, so I can continue where I left off if a computer fails.
A Time Capsule backs up my computers, except my iMac which has its own dedicated drive due to the amount of data on it.
Large data such as RAW photos and video and my music library, which can’t fit on the Time Capsule or in Dropbox, are backed up manually (or when I was using Aperture, using archives) to 2-3 other hard drives.
Lastly I have Backblaze backing up my iMac’s main drive.
Some thoughts: I don’t like the idea of using a NAS. I had a WD external drive which, if the hardware died, the internal drive wouldn’t have been readable by anything. This is absolutely no good. A backup needs to be recoverable easily if it fails.
Secondly, backing up to a multiple-drive array adds a greater potential for failure. About the only solution I’d consider would be a RAID 1 or RAID 10 set-up. I’d only consider an array if it were a professional solution for a business and I was rotating the drives with new ones once a year or two.