Cool stuff- Here are some things that stand out to me:
-like mentioned before, your chest topology is all over the place. Like in the image above, I would run loops around the deltoids and under the pecs, with vertical loops capping the shoulder and running down the arm.
-You could easily cut down your tris by making his skirt strips rather than a bunch of tiny cards. Your silhouette isn't benefiting from this nearly enough to make that cost worth it. You're also limiting what you can do by the card's shape.
-You don't need to have the holes cut into your shoulder pad - much like the cards, the "low polyness" of it is actually probably hurting you more than it's helping you.
-The eyeballs could be lower resolution and can actually be half spheres if they aren't already as no one will ever see the back of his eyes.
-In general, this model isn't reading like a 10k tri character model. Personlly, I believe that you are devoting a lot of geo to areas no one will care about (eyes, panels, gear detailing, etc.) rather than to things that could enhace the character's silhouette. Right now, you have giant, polygonal spikes jutting out of the character that could really benefit from being smoother.
-Your Orc has no wrists! The transition between forearm to hand is really flat. Try bulking up this area, making his hands bigger, respecting how the wrist bones would protrude outwards and - if you feel like it - dropping the hands out of a flat pose and more into a relaxed, "natural" pose will really make them read better.
-Everything is reading as if it is made of the same material. Give the materials some specularity differences: It's hard to tell if the gear is made of bone or metal. If it is metal, rather than painting in highlights, paint the diffuse black, give a high specular power and play with a specular colour (Metal is a highly reflective surface and generally is black, unless painted, the end result is the chemical makeup and how / what it is reflecting on it's surface.) Leather and skin should also have some amount of sheen - but be careful not to make it too glossy.
- Your skin shading seems really baked in, and even slightly random. For example, on the face and hands you could get a little more fine tuned with the detailing rather than just a flat brown or green. In general, your character could benefit from different skin tones - showing where blood would be closer to the skin, maybe where he's had sun damage, scar tissue, etc.
-If you could, grab some shots from Marmoset that shows "just" the different maps (diffuse, normal, spec) so we can better analyze what your maps are doing.
-Personally, I would lose the eyebrows To me, they seem to make him look friendly as the expression seems very welcoming. If you removed them completely, it would add a creepier / more menacing feel.