The good news is that you have a small but reasonably proportioned figure.
The bad news is that you have a small but reasonably proportioned figure.
Welcome to the tough choices between readability and realism.
I don't have Diablo installed on my machine at the moment, but I did have some screen shots from Titan Quest sitting around (It's an action RPG like Diablo II). The figures there are 1:6 head height to total height. Just a point of reference.
I like the armor texture that you have, it looks really good.
I don't get why the female's thighs are unprotected.
You could widen the male's shoulders by a pixel to help distinguish between the figures. Or make them 1 pixel more squarish.
The nude figures are a bit flat, but if they are meant to be paper dolls like in an inventory screen then that's ok. Similarly, the pose is flat rather than a bold dynamic stance. Again, ok for some parts of a game.
Consider working on a neutral background color (like gray 128) rather than black. A black background can throw off your eyes.
The site
http://www.human-anatomy-for-artist.com/ has some refernce images of people posed with weapons. Might be useful.
Consider adding some color or accessories to the characters. An additional color theme would help grab the viewer's attention more strongly.
Hope this helps,
Tourist