Wow, a lot has happened in this thread, but I'd just like to say that part of me is happy that Ninja Theory has moved on from DmC. With DmC, they became a studio I could really appreciate, and with Hellblade they won't have to deal with the backlash and fear of doing justice to an existing franchise.
In a way, despite it being a fairly different game, Hellblade is the future benefit that DmC guaranteed us. Even if we don't get a sequel, I know we'll get plenty of awesome things because of the experience and freedom NT now possesses.
You know, I've always wondered how they did that at that time. That effect is really cool.
You copy the existing mesh (his head), push the polygons away from the surface slightly so they appear to be just above the skin, then apply a separate texture with an alpha channel on top of it. The texture is subsequently animated. You could even do this on the N64, although of course semitransparency was avoided back then.
So the answer is that there is an additional mesh on top that is animated along with his facial morphing. It was certainly a risky approach to the character design at the time, which I appreciate a lot from a technical perspective. Even still, it was near the end of the PS2's life cycle, which explains why they were able to polish the graphics to the extent that they did. I think Final Fantasy XII was one of the only better looking PS2 games.