Re: "companies should consider building redundancy into their cloud instances"
I think the author misses the point slightly, and states the bleeding obvious Of course, any implementation with any value should be resilient, but each AWS region includes multiple availability zones, each containing multiple datacentres. Any deployment with resiliency across those *should* be resilient, period. Amazon make the point that replication within a region delivers HA/DR, is fast and free. Replication between regions adds complexity, is slower (as it's over the public internet) and costs, if only because one of the core tenets of cloud is paying for data egress out of the source.
To put it another way, how many of you have your on-prem DCs spanning different regions? Off the top of my head, I would have to go back 7 jobs to find a place that did, and most of those are big enterprise shops.
I think one possible takeaway is that Amazon's position that you don't need to deploy into multiple regions is now called into question. If I worked there, I'd be pushing for a new service in the form of direct connectivity (not via internet) between regions, with a lower price point for data transfers. AWS do offer this kind of connectivity to customer sites, but presumably anything between regions would be a fat pipe not specific to any single customer.
Alternatively, perhaps the fact that so many orgs tried to all failover at once is key, in which case maybe AWS needs to review it's provisioning/overcommit policies.