Thanks for the feedback everyone.
Mr. Blonde, thanks. It seems I only receive crits like this once a year.
Though I wasn't intentionally trying to shy away from detail in the fourth piece, I can really see where I dropped the ball. The presence of black in the painting was some attempt to be unsettling and ambiguous. I wanted it to be repelling in the same way that darkness was when I was a kid. (I was kind of a cowardly little kid FYI) But in the places where light is present, I admittedly reveal rather sausagey forms. Given the subject matter, you can probably understand why some of the proportions are askew. I do wish that there was a way of making the foreground character's shapeshifting arm read better without some stupid aura, however. I had hoped that the remnants of a hand at the end of the blade and a blistering forearm would do it, but some people just don't pick it up.
On digital art... If you have a lack of fundamentals I don't think any program, tool, brush, texture or method in the world can save your piece. That being said... I havn't made a traditional piece beyond a study in a long time. When i'm trying to learn something I always do it on paper or canvas, though.