They don't scale automatically to your level, you have to pick the right instance. You used to need to do access quests for the 2 first instances (30's and 50's) but not sure if they took those quests away with all the other ones or not. Quest for Return to Nek Castle was called Putting Maltena to rest, and the instance of Nek Castle was way different than the original one, there was only 1 way to go, was pretty linear, but quite fun and challenging at the time. Im hoping it is challenging this time around too, and not only in a matter of having mobs with a buttload of hps which is sadly often SOE's perception of a challenge.