I played nothing but defenders on live and I don't know if their gameplay changed on HC but I've always considered my rad/sonic a duck treading water. Calm on the surface, kicking butt underneath the water. I doubt that's changed much but what did change is my taste for gameplay styles.
If defender isn't your cup of tea, it's better to stop now but keep the character until you want to pick it up again, because you will eventually get that itch. Try some other ATs and find one you like. Don't quit, just explore. You may come to find you like your defenders' impact after all.
Have fun out there...