“Proper backups” imply that you have multiple backups and a backup strategy. That could mean, for instance, that you would do a full backup, then an incremental/differential backup each week and keep one backup for each month. A bad cable would cause you trouble, no doubt, but the impact would be lessened by having multiple backups points spread over months.
Redundancy is not backup. Read that again.
Redundancy is important for system resilience, but backup is crucial for continuity. Every filesystem is subject to bugs and ZFS is not special. Here’s an article from a couple of days ago. If you’re comfortable with no backups just because you have redundancy, more power to you. I wouldn’t be.