The big dogs absolutely do phase config rollouts as a general rule.
There are still two weaknesses:
1) Some configs are inherently global and cannot be phased. There's only one place to set them. E.g. if you run a webapp, this would be configs for the load balancer as opposed to configs for each webserver
2) Some configs have a cascading effect -- even though a config is applied to 1% of servers, it affects the other servers they interact with, and a bad thing spreads across the entire network
There are still two weaknesses:
1) Some configs are inherently global and cannot be phased. There's only one place to set them. E.g. if you run a webapp, this would be configs for the load balancer as opposed to configs for each webserver
2) Some configs have a cascading effect -- even though a config is applied to 1% of servers, it affects the other servers they interact with, and a bad thing spreads across the entire network