I notice you take the effort to visualize your characters in 3D before drawing. Instant +10 bonus points.
That being said.... you seem to have the same problem as me, which is that the poses need a bit of work. (Your newest one is better than the rest, though.) The inimitable Merekat has, in the past, suggested the use of photos for pose reference, rather than imagination or (worst of all!) posebook/copying - I haven't tried that out much, but she's probably right.
Have you tried CGing as an alternative colouring means? It's pretty cool - if you can get your hands on an inexpensive graphic tablet. (Those things last - I got one back in '00 and it's still alive and kicking. Best present I've ever received.)