I think the big issue is that characters with flaws are different from straight-up dicks.
If you make a character purely to be a dick, all you're doing is just making a dick. Not a character. Same reason why you're not making a character if you aim to make "cute girl". Making a character means figuring out the various ways in which a character mentally operates. Their likes, their dislikes, their goals and aspirations.
Willis, to his credit, has some good sensibilities in terms of his characters. They all sound different in their own way. You can feel that these characters have different personalities and a different tone of voice, and aren't just a telephone to portray Willis's opinions....more or less.
It's when he needs a villain that he tends to crash. He can't have ambiguous characters. He needs things to be black and white, clear as day, that we need to be rooting for this character and not this character. If you have a character that could be ambiguous, and you need a good villain, you will be easily able to inflate their flaws to villainous levels.
And that's fine, a story should have a protagonist and an antagonist, conflict and all that. Not every story should be a gray morality commentary about how the two sides aren't always right or always wrong. The problem is that if you keep recycling the same shtick repeatedly, people are going to notice and rightfully complain. He shouldn't aim to make the next great epic, but he should be aiming to make a better overall comic.
Not that it matters what I'd say. I'm from 4chan.