Does this location have strict separation of DBA vs. Dev duties? If so, it's possible they want a senior on site for the one-off "HOLY CRAP ITS ON FIRE!" events, and generally they've found they need a lot of experience for those moments. In between, they're there to support the devs with the mundane crap and make sure the architecture stays sound.

I agree it's definately worth a discussion with the managers as to their expectation to the role, but go in with an open mind. Leave your expectations at the door, and be willing to discuss ways you can help in between the duties they want you to attend to. I agree with Sean in this, be careful of your wording, you're the new guy.

Hypocritical Refuge: That's advice from the most tactless person on the planet, I know, which should probably tell me something about myself. However, I'm used to being the one called in to come fix everything that's falling down around people's ears, so my typical approach is not one I'd take towards a longer term position.