nc-customer

So namecheap would need a few different, separate IPv4 subnets.

Like the ones they already have?

http://bgp.he.net/AS22612#_prefixes

If namecheap chose to stop assigning all customers the same list of DNS servers, it would benefit namecheap as well. There's 200+ people in the queue for live chat right now :)

It's not DDOS mitigation or H/A, or some other high end feature.

They could better protect against it by not assigning the same list of DNS servers to every customer.

I suspect the hackers are targeting one of namecheap's customers, not namecheap directly. Because that's usually the case, a good approach is to not give all customers the exact same nameservers.

Most DDOS attacks against a company like yours are actually attacks against a specific customer. If:

a) you had a pool of DNS server names, say 20, all with unrelated hostnames

b) you assigned 2 to each customer, randomly, when they configured a domain to use your servers.

Then, a DDOS attack would impact 10% of your customers instead of 100%. (Assuming other practices, like null routing the target until resolved)