One of the problems with Raid is the drive itself is in the PC. In case of a fire in the building, the drive may be compromised. I have seen drives survive fires to be cloned to new ones on many occasions. I have done so for several customers.
For a piece of mind, having a backup off site is nice. The problem with that is the backup usually only consists of the data and not the whole hard disk in bootable form. You would have to reinstall all software, all settings and updates before being able to restore the data.
In order to keep from having to do that, you would want a hard drive cloned/backup but it takes quite a bit of time and space to create as Windows bloats itself, along with all the programs and data.
With Raid if the database gets a small corruption that eventually leads to a crash of the database, that corruption can be mirrored also. I have seen several times that a restore of a back up led to a follow up crash. To get around that multiple backups can help.
So what it gets down to is, how valuable is you data. Can you restore all the programs, updates, drivers... and data. Do you have the time for lengthy backups...