Aside from a few things some of the people have said, (some are correct and some seem to be opinionated) Destiny's foundation of character related roles and stats remind me a lot of Dungeons & Dragons (the original book and paper game). Your enemies are clearly modelled after traditional RPG roles so why not your role, too? Warlocks are your mages. Mages are supposed to be low armored but given the opportunity to reward the patient and smooth players. Hunters are your Rogue class. Quick low armor with higher agility and maximum damage output if patient and precise or a little more of an archer type with more armor and less agility. Titans are you warriors. Typical tank. That should be obvious. Im happy with how it turned out. My opinion may change once my warlock is fully leveled but, I've not found any reason to even remotely say they're an underpowered class. Just my opinion, though.