Does Paul ever describe church-age believers as sheep and Christ as their shepherd?
No. Paul never uses the illustration that church-age believers are sheep and Christ is the shepherd, and no such verse can be shown. Instead, Paul presents every believer as an intrinsic member of the body of Christ, connected to the Head, which is a far greater position than a sheep under a shepherd.
Les explains that Paul never uses the shepherd-and-sheep illustration for church-age believers. Every believer is baptized into one body, the body of Christ, which is likened to the human body: the source of all experiences, emotions, thinking, and all that is in the mind, yet the mind remains in control of every facet of the body and responds to it. So it is with the body of Christ — every believer is connected to the Head. Les stresses that this is much greater than being a sheep out under a shepherd; we are part and parcel of the Head and the body. He notes that this makes all the difference in the world and we dare not diminish it, because this is what Paul does in Ephesians, Philippians, and Colossians especially, taking us into a higher plane of the Christian experience not found anywhere else in Scripture.