There's so much that has an impact in answering a query about "dev's as DBA's" that there really is no straight answer. I've found that companies need to grow large enough to warrant a DBA, and that many dev's can do a reasonable job of DBA work in the interim (though unfortunately, the reverse is not always true.)
In my career I started off as a developer and made a conscious decision to follow a database-specific path. At one role after I just started I "met the team" of developers and explained my career history. One developer was bewildered that I would turn my back on VB and pursue databases. To them, this was akin to Anakin Skywalker turning to the Dark Side. (As Yoda might say, "Is that set-based logic I sense in you?") But therein lies, for me, a very important distinction in mindset. For a developer a DBMS can be reduced to a fancy flat file. Tables are just a form of TXT file, and SQL Server is just an Excel document with indexed worksheets.
As for support, I'm not sure I'd agree with rotating DBA work. The fact that it's rotating suggests to me that no one really wants to do it, and if they don't want to do it then what sort of a job are they doing?