Idea is great !
Hence, i'm not completly fan of the front legs. They look too much like arms. A four leg animal should, i think, put them between each of the rear legs. And not "in the air in front of him", like arms.
Think you would have a more "animal" look by doing this. When i saw the picture at first sight, i thought it was a creature with four arms and that was all.
As for the GS work, and thhe general proportions, it's right. I think you get the point. The idea to chose aminotaure is excellent ! Position of the armes is good for a character. And the weapons are ok too for a great Dragon Ogre.
Will you give him special abilities ? Will it be a character or part of a unit ? I would see him as a character.