Wow! Amazing! The tutorial you linked to is MASSIVELY helpful. That 'rule of thirds' factoid was something I know I must have stumbled through in art school, and kinda neglected, and then seeing how you use it in this composition makes the entire concept CLICK. It makes SENSE.
By the way, for your 'inking' lines on Joker, were they a single color? Or a different color that is darker than the color surrounding it?