Honeytree And the condition of a backup can and should be known by TESTING them frequently. I'd argue that most organizations don't do this properly and one day they will get unlucky. The only way to know a backup is good and useful is to test your disaster recovery procedures with said backups.
Really sucks to find out the ransomeware that caused the disaster already infected months of backups or they are corrupted in some other way. Or more specific to Enhance, maybe version 11 backups don't restore so well on a version 12 fresh installation.
As to cPFence #2-3 your backups should be completely seperated from each other. Everything related to backup #1 should be able to disappear and not affect backup #2.
For example, backup #1 provider's entire network could go down worldwide and a volcano erupt under the region where my data is stored. Backup #2 is still safe. Half my clients probably won't be needing their data anymore but... I did my part lol.