They regularly are unable to create new droplets [or other control issues where you can't perform normal functions with normal latency] and/or have full DC outages.
Pretty much any use case where I'd use something like DO being unable to create new VMs, etc. is the same as an outage.
I asked why as I work for DO's operations team and I wanted to know what your concerns were. Do you have a specific instance of a problem? What you're describing would be considered a MAJOR outage for us and we have not had one in quite some time.
That is annoying enough I'd want to be able to failover if it exceeded 15 minutes. I get it might not be an issue for anyone else but failing over is less complex than mitigating latency issues with droplet creation or whatever.
I get "regularly" to me might mean something different to you but if the 2 DO DCs I was using are hit literally every month with a problem of some kind...it seems regular to me.
Pretty much any use case where I'd use something like DO being unable to create new VMs, etc. is the same as an outage.