I’d disagree, you have plenty of people who have been seen in recognisable things. Couple of them from coronation street, gaynor Faye, joes girlfriend was in line of duty etcWell when you compare the casts to the first three series, it's a pretty weak cast full stop apart from Neil Morrissey, far from recognisable actors.
S1. Timothy Spall, Matthew Lewis, Joanna Page
S2. Sally Rogers, Siobhan Finneran, Alison Steadman
S3. Lenny Henry, Melanie Hill
Apart from Neil Morrissey there isn't really a name in the cast you can send out to hit the promo trail.
According to IMDB Joe is in 6 episodes, but that could be wrong. He has definitely been pushed too far to the front for the promotional work compared to how much he is in the show.
it feels to me like joe was simply cast for the publicity. Fair play obviously he’s not going to turn it down but he wasn’t great