User blog comment:Spartian300/Why Titans are the best class/@comment-32856285-20140918210056/@comment-24057866-20140919152855

Except that Warlocks are not healers, Titan Defenders are better at support, and Hunters' abilities do not give them higher DPS than other classes.

You can't pigeonhole Destiny's classes into traditional MMO roles because they weren't designed like that. In a traditional MMO, every class is necessary because no class has all necessary abilities. In Destiny, classes aren't set up like that at all; every class can use the same weapons, every class can double-jump, and every class has grenades. They're all the same except for damage type and a few minor, near-aesthetic differences. A team of all Bladedancers will be about as effective as a team of all Strikers. A team made up of multiple classes will be about as effective as a team made up of only one class.

Bungie specifically designed it this way so that no matter which class you prefer, you can still play with your friends in both PvE and PvP and your fireteam is not hindered. Bungie did not want to create situations in which a group of friends will be hindered in their effectiveness because they all chose the same class.