What does ZFS have to do with this? This is like any other properly executed backup. You may as well call it "defeating having your day ruined by keeping proper backups". Granted I do like ZFS and I've literally been doing this for ages, backing up my KVM guest images to ZFS SAN the KVM host can access to save the snapshot and the KVM guest can't access at all.

However this can be done a million different ways. It's just a backup not accessible to the affected system... I do the same thing with my bare metal OSX machines (macbook, macpro, etc...) they use time machine to backup to Netatalk shares, those shares are image files which again get backed to the ZFS SAN. So even if the time machine share was encrypted I'd have a copy of the image holding the share from X days ago.