My production team does all the tasks you mention for production. We also work with, but do not have the primary responsibility for, all the tasks you mention on the development side. We are a large Site so the division is natural and works well most of the time.

Some of the Development DBAs will work on a production DBA task from time to time, but their funding is project specific so they tend to have a much narrower focus than the production team does.

We have other contracts that we support that are much smaller than our main IT contract. In the small shops hybrid DBAs are more common. Of course those environments tend to be more chaotic since they often lack formal change control. Configuration management is left up to the individual technical person doing the work. Generally, nobody checks the work of a hybrid. This can be cheaper in the short run, but generally costs more in the long run as each generation of "hybrid" cowboy gets to figure it all out all over again.