Fortunately, I had a backup.
Well, good, because (as anyone who is considering running RAID should know) RAID is not a backup! "RAID" and "backup" are mutually exclusive. As you point out, RAID is only useful when you need high availability and ability to recover from drive failure with minimum fuss. Your horror story was caused by trying to build a RAID5 array (only one drive's capacity of redundancy) on a computer where the loss of either of 2 controllers meant the loss of the entire array. And using cheap controllers, on top of that.
Backup is for when your primary copy (whether it is a single drive or a RAID, it is still a "single" copy) fails for any reason at all.