The reason you will still need old Dusk is that the HW hairs, Hero and Mid Length for Dusk, break and/0r deform when using Nataani by COF, and Joe and Jackson in the Rodrigo pack by CWRW.
I've been looking at this. In Nataani's case, there are solutions with the hair fitting of the HW hairs.
Dusk's Mid-Length hair :
1. Load Hair
2. Conform (Fit-To) Nataani
(This is assuming Dusk is already loaded and Nataani's shape preset is loaded.)
3. Apply the "Dusk Head" and "Dusk" morphs to Nataani.
(First one is found under "head" and second under "body" of Dusk SE.)
That should be enough to fix the fitting of the mid-length hair for Dusk. If people still find that the hair is colliding into Nataani's neck, I have made a morph for the hair that will move just the bottom rear of the hair back away from his neck, and I can release the morph if needed.
For the Hero hair :
1. Load Dusk, apply Nataani's shape.
2. Load and conform the hair.
3. Apply both the "Dusk" and "Dusk Head" morphs to Dusk SE.
4. Now select the Hero hair, and go up to the top of your DS window. Click on Edit --> Figure --> Add Smoothing Modifier.
5. That should be enough to get it fitting Nataani's head. You can adjust the Smoothing Iterations and Collision Iterations of need be.
I do not know if this is an issue in Poser, but this is how I got it to work on Dusk SE in Studio.
Here is a screenshot of my settings for the smoothing modifier if it's needed...