Fourth Update: Retopologized & baked the AO & normal map from the highpoly sculpt in ZBrush.
It is now optimized to the allowed polycount set on the Dota2 workshop page, and rigged & skinned so it is working with the animation ingame already.
These images are the result in Maya after applying the new textures. I really like the result so far. Next step is colouring!
Head: 800 tris
Neck: 400 tris
Arms: 500 tris
Belt: 700 tris