I like that one, its simple as you said but looks like some sort of mercenary that is between the bandit model and the Footman. As mentioned above, I'd maybe resize the hammer a bit to make it more noticeable ingame while being moved around. Also I suggest using one of Usimajas optimized models for it; with them you can make it only use one model as the portrait is build in.
The head just adds the weight and is used for knocking people silly. It doesn't actually puncture armor. The spiky bit at the end is what puncture armor with the help of the weight on the opposite end (works a bit like a battle axe).
It's a very neat alternative human infantry model for those in the market for a rougher aesthetic. I agree with everyone saying the hammer is too realistic for Warcraft 3. I get that you were aiming for a realistic aesthetic, but Warcraft 3 doesn't abide by those rules, and the result is a horrid clash of styles that leaves everyone unsatisfied. I recommend bumping it up to the cartoonish standards of the game. The only other change I would suggest trying out is maybe playing around with the type of helmet he wears (there are a lot of interesting medieval helmets out there, and very few of them are represented in Warcraft 3 - a bucket style helmet, or a half-helm, could look cool). Good work!