I dont really count anything that happened as filler, but I can understand what you mean. However you have to remember that 2.0's story was designed to be done across 50 levels and take you to each part of eorzea as you reached the level you were meant to be in that zone. You were supposed to do it as you levelled up, without having to wait to get 10 levels each time before you could do the next quest or grind a whole bunch just to see the story. We couldnt really have earth shattering battles and mind blowing revelations at every single level. I imagine the expansion story will probably not be as long, but will be designed for high level players and wont need as much of that 'filler.'