Even the old school 3 die sets had taper ( or roll ) crimp. And it was still applied in the "last step", albeit more than one prosess was taking place during the said Last Step.
The other, other thing is despite the functions being combined on the same physical die, it was (is) possable to perform the steps separately. Back the die body out of the press, and lower the seater to seat the bullet before the case contacts the crimping shoulder, thereby the bullet is seated without any crimp. Then screw back in the die body, but raise the seater so it doesn't contact the bullet even when shellholder at the top.
Yup, a lot more hassle. *Most-* of the time the seat & crimp in one step works acceptably, but sometimes for specigic bullet/ brass-/ load, seperate is needed.
As to the OP; IF his crimp die is in spec, and the brass isn't very thin necked, and the bullets aren't undersized, the most likely suspect is the case expander. Specifically being too large, leaving the sized neck ID too large, thereby giving insufficient neck tension.