The Twins are a team of many needs.
Doumit fills the need of back up catcher and emergency RF. He hits well for a catcher, but at best adequately for a DH or RF. He doesn't defend well at either spot. As he declines, his best role will be back up catcher and pinch hitter. He will do that job well. He will be a good guy in the club house.
Essentially by signing him now, they have begun the winter process of rebuilding this team through free agency. Is this the best first