HulkSmashedEdit

I think some of it stems from you using yourself to model a head design. You have one of those heavy hero jaws, you tend to draw your jawlines very heavy. With the Hulk it fits. But look at your other stuff. Start playing with different head shapes. Like the Joker is traditionally triangular head.

There are a few basic head shapes oval, round, squarish, heart shaped ( females mostly ) triangle. There are more but not off the top of my head.