Destiny Factions and their Roles

I was thinking Bungie would go down this route of classes/factions. But it almost seems like they had abandoned the previous symbols (seven seraphs, osiris, dead orbit, etc). I was hoping for some insight in THOSE factions but instead we got a whole slew of other things. I'm thinking it will be handled in the same manner as Dark Souls handled PvP and PvE, but on a larger scale. I think that we'll be able to raid "heroes" trying to complete a mission by using the enemy factions like "The Fallen". Hopefully with Private Groups we'd be able to stage these invasions/raids on a much grander scale.