No, it just blocked IPs from DoS traffic because it was easy to identify... customers ware unaffected. If you can block anything that sends you more than 200 requests within a minute you are off to a good start.
It depends on how many nodes DoS is coming from though, as if it's coming from 1,000,000 nodes, it would only need to make let's say 5 requests per second and it would saturate network, and no firewall would effectively stop it. However, if DoS is going from 1000 nodes with 1000 requests per second trying to saturate your network - those types of DoS will easily be dropped by almost any properly configured firewall.
Essentially, I agree that if DoS was as large as what brought Sony to a crawl, then only good planning ahead could negate it. It involves a lot more than a firewall. But if you are running medium sized business, and it's some script kiddies that are coming together to try and bring your site down through DoS, it can easily be negated with a proper firewall.