"Seems like a nerf to me"

Its a dual mechanic. The point of staggering it's implementation a few levels apart is to get used to the fourth tier combo with the new rotation first and then be introduced to the increased difficulty floor of the mechanic later. Having it all dropped on you at once would be a bit crucial. So they broke it up to allow you to ease into it. That isn't a nerf, it's the intended mechanic for the fourth tier combo. Dragoons can put out massive amounts of damage now and to offset this complexity was added to their positionals.