Solar Hero Style
As always, I am not the developer, so my answer isn't the "official answer" but here is my view:
Adamantine Fists of Battle works like Pounding Hammer of Devastation Technique, except better due to being scene long and causing levels of damage to living and inanimate targets. As such, it follows the Pounding Hammer Charm's explicit note that it adds its bonus to the raw damage of the attack.
In the case of the Pounding Hammer and Adamantine Fists Charms, this results in the potential of a mixed pool of dice and health levels of damage. I would have the soak take away dice before health levels, in this case.
As always, I am not the developer, so my answer isn't the official answer but that is my view as a role-playing game writer and longtime Exalted Storyteller.
