Titans have either a debuffing grenade which is incredibly useful in hard mode, or a huge bubble to protect your team, which is again incredibly useful. Warlocks could cheese Atheon, thus everyone wanted them. Now though they just have the ability to revive themselves, meaning if you all wipe you get a second chance without going back to checkpoint. Hunters have nothing beneficial to teamplay. The job a hunter does any other class is capable of at the same time as having the aforementioned abilities. I'm a Hunter by the way.