«The provided backup tools are sufficient!»

This can be sufficient as long as the backup tools ensure that the backup stocks are unchangeable.

However, if you do it yourself, you should make sure that the process is verified by an independent body, that substitutes are in place for absences due to holidays or illness, and that the necessary time and resources are available. If one of these points is not feasible or difficult to implement, an external, proactively managed service is a good alternative.

With such a service, however, it must be possible to guarantee that the service provider will not have access to your data – ever.