The biggest time save is in time spent recovering. It's so much faster to restore the entire system than to reinstall the OS, reconfigure the bootloader, resetup disk encryption, reconfigure user accounts, reinstall all software, manually reload configs, etc.
Or put it more directly, full disk backups are a great way to get RTO down.
Agreed. It was a large time investment that happened to pay off. If I ever have to do it again I'll be much faster. I hope that with wider ZFS adoption some of the routine tasks will be automated better in the future. I see no reason why in a couple years this couldn't be a mature fire and forget user experience.
Or put it more directly, full disk backups are a great way to get RTO down.