Splitting A Mirror - RAID Is Not A Backup, But Should This Work?

In one of my calls with Technical Support after sending a Tech Support Report, I was told that I should not have created four separate disk volumes on a mirrored pair of 16TB disks. The discussion then led to considering buying even more disks to offload everything, delete the mirror volume, and restore to a new, single mirrored volume.

But knowing SoftRAID quite well after everything that just happened, with the understanding that RAID is not a backup to begin with, is there any compelling reason why I should not just split off the secondary disk of each volume a non-RAID volume, delete the 4 disks volumes on the primary, then create a new single volume on said primary, transfer the data onto this new primary containing a single volume, and then convert that volume into a new mirror at the end?

Of course I'd confirm full backups prior to this. It wasn't really clear to me how backing everything up to a single new disk and then wiping the mirror would be any more secure than splitting the mirror using the pair already here. Isn't the vulnerability of a single-disk the same either way? 

But I believe that all those volumes are already on other disks in-house (making the mirror already a backup) and I'll check the offsite disks to find out about those too before doing anything at all.