Every class is DPS according to Bungie, and every class can pretty much do every thing. Your choice in class is more of an emotional choice in how you want your character to solve their problems. For example, if you wanted to make a build that specialized in AoE damage and crowd control, a Warlock might do it using fireballs, a Titan would create a shockwave with his fists, and maybe the Hunter would lay a trap. We don't have more specific details than that, but the Warrior / Wizard / Rogue Archetypes are very fleshed out in other games, so pick what you've enjoyed playing in the past and go for it :)