I think the bottom line in your quest for a new DBA is that it's hard to find people who have a broad understanding of the issues surrounding any given technology. I often meet DBAs who can't design a schema, because they've spent all of their time tweaking tablespace allocations, implementing backup tools, etc. Many people in IT have a very narrow world view, and I think it's particularly bad for DBAs. In my current job, I have discovered that I am often the only person on the team who bothered to read the manuals for tools we're using. I make suggestions that come straight from page 36, and people think I'm some kind of Oracle guru. It's a bit disturbing, especially since they still won't read the manuals.
Anyway, I think it's much better to hire people who have a general understanding of at least the technologies they are responsible for. I would ask a DBA candidate questions about normalization, deadlocks, isolation levels, scaling strategies, and other fundamental database issues before I got into how to tune SQL Thingy v.90210 on VMS.