Having been burned in the not too distant past, I am not a fan of RAID. RAID is for commercial use when you need data up and available 7X24X365. This is not the case with Lightroom even for professionals.
You do not need redundancy. You need version controlled Back up In a redundant file set up, it you delete a file on one drive, it gets deleted on the redundant drive too. If you later discover that that file deletion was a mistake, tough!. The same is true for file changes. You can't recover the state a file was in 6 months or 6 weeks or 6 days ago. Cloning is not a valid backup solution. IMO, nothing beats Apple's Time Machine for backups. It backus up all of your critical user data from multiple drives to multiple destinations (the backup destination disk needs to be large enough to store all of the data on all of the drives being backed up. In the Windows world Acronis comes close to matching Time Machine in specs and performance. A good backup app runs in the background on a schedule. So you do not need to baby-sit the process.
My TimeMachine backs up my Primary volume and my Lightroom Data volume. It alternates between a destination on my NAS and a locally Attached volume. This is for redundancy in backups. Time Machine on my wife's MBP also backs up to the same NAS.
For complete insurance against fire, flood, pestilence or civil unrest, a cloud backup is recommended. I use BackBlaze. For ~$100 a year you get unlimited backup and 1 year of version history. For the price of your LaCie 2Big Dock, you can have 12 years of BackBlaze backup.
I'd keep the backup volume that you have and perhaps get another (NAS?) for duplication. Add a BackBlaze Subscription. Put the other $1100 in the back for future years.