Looks good, If i were you I'd start b sanding it ALOT. Asin, til its smooth, and a perfect "Cone shape". Or lambshade shape, seeing as in theory, despite all the details it is the basic shape.
Once I would have done that, I'd sketch some blueprints from ingame pictures, or just print off some pics of the helmet.
And add every detail bit by bit.
I'd start by working on the gas-mask pieces. And the two side ones, they look better rounded, not hexagonal.
Oh wow, it was you Instructables post that gave me my first insight in how to make armour, it's awesome that iv'e found more of the helmet progress on here now.