how good/bad is a RS/CC Pinsir ?

Bad idea, people talk about Machamp so much b/c he also resists both dark and rock. Pinsir is weak to rock and obviously a fire blast will fry a Pinsir, so a huge liability versus Tyranitar bosses.

Not ideal for any of the raid bosses, but he has a high att stat so he still hits hard...

Generally better to attack into psychic types...Will be hurt bad by Tyranitar, but he is still serviceable in terms of pure DPS...

That said, he doesn't resist (or immune) to psychics neither so you're better off with Houndoom (seems hard to get for a lot of people, but very common in the desert...).

Before I got a Machamp (or primeape, even my poliwrath was double water), I'd use a Lv 26 RS/CC Pinsir for Blissey and Snorlax, but when I used him the other day in a raid, one hit from Ttar and he was gone.