Titans are not the weakest, but they're certainly the most disadvantaged. Both subclasses for both warlocks and hunters can be deadly in crucible, hunters especially. Defenders are the most disadvantaged of all; who in their right mind thought it was a good idea to have every other super (other than radiance and another bubble) outdo a ward of dawn?! Voidwalkers can bomb the bubble, strikers can smash the bubble, gunslingers can shoot the bubble, and Bladedancers can do their annoying shockwave thingy that travels straight through the bubble. If any class is worthy of a PvP buff, it's defender. On the other hand though, striker is a very powerful PvP class, and all titans have great grenades.