They timegatted the exotics this time because with HoW and TDB people had almost all of the exotics (non-POE, Non hard raid) within the first 1-2 weeks then started complaining about having nothing to do. That proved how limited the content was, so they fixed it by releasing timegatted exotics. This way no one gets all the exotics within the first 2 weeks and you can't complain about having nothing to do because just as the game gets boring and you think you have everything...BOOM time gate opens and another Quest exotic happens.