Catalyzes the interconvertion of dTDP-6-deoxy-L-talose and dTDP-L-rhamnose. The equilibrium is strongly toward dTDP-L-rhamnose. dTDP-6-deoxy-beta-L-talose = dTDP-beta-L-rhamnose kcat is 0.9 sec(-1) for dTDP-6-deoxy-L-talose. Optimum pH is 7.8-8.4. Bacterial outer membrane biogenesis; LPS O-antigen biosynthesis. Belongs to the NAD(P)-dependent epimerase/dehydratase family.