Is there any way you can change the time of day you're playing? I tend to play late at night and the number of players farming dragons decreases drastically. With fewer people in the group the dragons take quite a bit longer to kill. Not only that, but I've noticed that the order in which they do things varies. Sometimes the iron atronachs spawn the first time he leaves the ground, sometimes later. But if you were able to play when fewer people were online you'd have more chance of the atronachs spawning when the dragon leaves the ground, because the dragon would take longer to kill.