I used Titan a bit in crucible, it's not any less powerfull than any of the other classes. It's all just a matter of utilizing your classes abilities, knowing the map, and using your super in the right area and at the right time. Defender was my favorite subclass in crucible, especially in controll. Pop your shield on a base, pull out a shotgun, and blast anyone that tries to come in and kill you. I've gotten pretty good killstreaks doing that with the defender.