My point is that if we have no OFFLINE backup, then a physical or network attack can destroy both our live data and our online backups at the same time. If I were an attacker, and I would really like to destroy a firm, then I would first target their backup system. If I can delete all backups immediately thats the best. If not, I would slowly poison their data, so their backups become useless. Only after that I would destroy live data. Therefore it is not enough if you have one offline backup, you must have several one, recorded at different times.
We do use replication, and we have standby servers. Those are useful for high availability. But that is not backup.
We also used offline disks for backups, but I find that inconvenient, and the backup software we use supports tapes much better than disks. I also do not trust disks for long term storage, see my other comment about this.
Until now we were the subject of targeted hacking attempts a few times every year, and they become more sophisticated as the time goes on. I am quite happy here, I want to keep my workpace safe.