It definitely sounds like they shouldn't have used datastore in the first place if it's giving them that much trouble. A common pattern we use is to replicate the data in bigquery, either by stream or batch job that flows over pubsub - perfectly scalable and resilient to failure.
I have noticed that people tend to get into trouble when they force the datastore to be something it's not. For example, I mentioned that it's terrible for analytics - there are no aggregation queries.
In the case of the tshirt retailer, I replicated a portion of our data into a database that was good for analytics (postgres, actually). We could afford to lose the analytics dashboard for a few hours due to a poorly tested migration (and did, a few times), but the sales flow never went down.
The datastore is not appropriate for every project (which echoes the original article) but it's a good tool when used appropriately.