So far so good, the unstable cards are hashing again and seem to be doing well. I also have 24x MSI 580 8G Armor's and using your methods have been hashing at or near 30Mh/s for 22 hours. This really is the best guide out there and I can't thank you enough for the thoroughness provided in your post.
ethOS has been the ideal OS for mining and the only thing I found lacking was notification services, so I built one. If you are interested it's currently in beta and you can sign up at ethOSOps.com. There is no installation as it monitors your panel and either sends you hourly notifications or immediate alerts. Here is an example of the hourly that I currently get, ethOSOps - Hourly Notification.
Thanks again!
Scott
RE: Basic Guide: Mining Ethereum with RX400/RX500 GPUs