Plenty of premium providers have outages all the time. Outages happen. Since you know nothing about the situation, I'd recommend keeping your assumptions to yourself.
A DNS provider that has set the DNS servers up right (and on seperate networks) should never have a complete outage.
When DNS goes down like this, you have not set it up right.
And setting it up right is not rocket science...
I'm with you here. Domain reg and DNS are their primary functions - Hosting etc are secondary. With DNS the way its designed your first thing should be getting your failover right on your DNS servers on different networks.
Their DNS servers are located separately (At least by IP / Subnet - Could be in the same rack with different data connections i guess) so why didn't a failure of their primary systems leave NS2 and NS3 working??