Many people struggle with the distinctions between visual designer and user experience designer. Are they real distinctions? Yes.
I feel this is one of the most important aspects of UX team hiring. Wireframers should add as much to the visual language of a UX design as the visual designer does, but they are not the same people. A team should have at least one visual designer who enjoys knowing the nuts and bolts of interaction and at least one UX designer with strong art school style critique skills. But who does the wireframing? Well, who's available?