This document is a great resource for setting up a UX team.
Seems like this is more biased toward the usability professionals. The numbers for interaction designers seems off to me for some reason.
For me, a well-equipped Interaction Designer also does Design/User Research, although I like to have at least one usability specialist type on the team. It can be helpful to have somebody who didn't do the design manage its evaluation. So I mentally combined the 2 usability and 3 IxDs into 4 IxDs and 1 usability. That's a nice number of folks! Plus then a visual designer, and an information designer. See, I'd say a great IxD is a strong information designer, too, so...that's a well-staffed team!