I wish you to remember one thing: during an interview for Kotaku between Luke Smith and Jason S, Luke admitted that they [Bungie] had no idea of what the Darkness was and the entire narrative core of D2 was going reboted. Which means that many things we've heard about the Darkness and other topics in D1 are probalby... well, wrong or they've been modified in the meanwhile. For example, we now know that the Stranger was a complete off-character so basically everything she said was just garbage. We've got more informations about th Darkness and what's going on into the Destiny world during the last months that in the entire Destiny 1 cycle. Also, the Vex = Darkness thing it's pretty unlikely under many points of view.