As is typical with this line of thinking, it only scales so far and only applies as long as you are "on the map" of what is standard. Stray too far and your devops personnel will spend more and more time "administrating" and less time coding. Being primarily a coder with considerable sysadmin skills, this has happened to me in every job I've worked in the last 5 years. I start out devops while everything is standard and slowly do more and more admin until I eventually quit (because I'm primarily a coder). The job I'm quitting this month is because I'm now 95% admin. Like all resources, you need what you need. Devops is sufficient is specific circumstances, but if you stray from that scenario eventually you need an admin. They're the glue when things don't quite fit seamlessly together.