Variety is the spice of life, So I hear...
From my experience with staffing small groups of people, utilizing everyone's skill sets in such a way that makes them happy with what they do is one of the most important things. Happy Staff makes Happy Customers.. If a staff member that is super awesome at one thing says that doing that one thing over and over is getting brain numbing and they'd rather do something else, work with them to see if there is something else they could do. As for the specific levels/departments that our company uses, we normally work with just sales/billing, support/admin , and abuse departments. Everyone works the departments they know and most learn the other departments eventually. It might sound like chaos, but a good balance of people who know what they are doing combined with a good manager to help direct things then things get done properly, on time, and everyone is happy.