Your claim is based on what exactly?
Btrfs' RAID-1/RAID-10 is stable since ages it just needed more than 2 devices since with a simple two disk mirror and one disk failed the mirror went read-only. Problem known, use 3 disks, done.
According to official docs this has been fixed with 4.13 now, status is 'OK' while read performance still could be improved: https://btrfs.wiki.kernel.org/index.php/Status
As I read the same page today, it says BTRFS RAID1 is "Mostly OK". When Dev's and their doc's say "Mostly OK", that does not equate to "OK". Still, to my surprise, there's been a change in a status since I last looked at it, which was just a couple months ago.
With reference to, BTRFS RAID1 unning in degraded mode (1 disk) and failing into a permanent "read only" mode. (Which was the primary reason why I refused to adopt it.)
As I dug into it (getting on the BTRS project mailing list), the Dev's said that they had corrected most of the problems with RAID 1, a few months ago, but since BTRFS is rolled into the kernel development cycle, there was no knowing when these fixes would be released and make it out into userland.
Here's the github pull request on July 4th, 2017 for ver 4.13. Have these changes made it out to user land yet, in normal release cycles? In the aggregate, unlikely. When will they get out? Who knows. (And the answers to these questions are not my opinions, they're those of the Dev's.) Progress has been "glacial".
As I see the BTRFS version on my own box, it looks like I have 4.7.3So, it appears that the RAID1 BTRFS instability, in userland, is still an issue.
So, in the way of practical advice for Blabla, I stand behind what I said earlier. (And I don't see "use 3 disks - done", as being practical for running a RAID 1 equivalent mirror.) ZFS is stable, mature and ready to go now, with a plugin that's easy to install, and it will require only 2 disks.