Too be a good DBA you do need understanding for other things than just the database. I'd say you should have some AD experience, OS experience. If you also have programming experience of setting up and distributing programs and building programs you'd be a even better DBA because then you are of higher value to the company because you can help the developers in a better fashion. Limiting experience to only one thing without no understanding of what the sql server is running in for a type of environment is a bit ignorant I'd say because having the bigger picture always provides a greater understanding.