Archetypes and the Hero's Journey
A better method for appreciating character relationships exists.
By far, the most useless aspect of the Hero's Journey mono-myth lies with the concept of the character archetype. The Shapeshifter, the Trickster, the Threshold Guardian...while romantically named, prove ultimately worthless to the working writer.
On the other hand, Archetypal Characters as defined by the Dramatica theory of story prove extremely beneficial. Here, characters are seen as functions, completely devoid of their relationship to the "hero" of a story. Protagonists pursue goals and Antagonists prevent them. Guardians help while Contagonists get in the way.
The Hero is nowhere to be found.
While there are some similarities between the two ways of looking at story, the mono-myth approach falls well short of defining all the archetypes present in a complete story. The following is a comparison of the two paradigms and the relative usefulness of each. It assumes you have a working knowledge of the Dramatica Archetypes.
First, let's start with the Campbell archetypes that are actually helpful:
Campbell: The Hero's function is to serve and sacrifice.
Dramatica equivalent: Protagonist - the Protagonist's function is to pursue the goal of the story. There are no moral implications associated with this function; the goal could be noble, it could be despicable. All that matters is that this character is the one pushing the effort towards the goal. "Restore order" could be interpreted as solving the story's problem, but again "order" implies some sort of assumed preference to things being orderly (sometimes chaos is the thing that can solve a story's problem). The concept of Hero is identified as the character who is both Protagonist and Main Character. The two are not automatically the same.
Campbell: The Mentor's function is to guide.
Dramatica equivalent: Guardian - the Guardian's function is to teach or help, and represents conscience. This one is pretty similar, although it's important to point out that the Campbell version assumes the Mentor is guiding the Hero of the story. The Guardian could be helping or teaching anyone. All that matters is that they objectively represent that function.
Campbell: The Shadow's function is to destroy.
Dramatica equivalent: Antagonist - the Antagonist's function is to prevent the goal of the story from being met. This too is pretty similar, but the idea that they have to "destroy" can be limiting to some writers.
Campbell: The Ally's function is to assist.
Dramatica equivalent: Sidekick - the Sidekick's function is to show faithful support. Again, the same.
Campbell: The Shapeshifter's function is to question and deceive.
Dramatica equivalent: While the deceiving part sounds closer to Contagonist, the idea that this character is supposed to supply "doubt" in a story implies that this character is the Skeptic - the Skeptic's function is to be the disbeliever - the cynical one who opposes efforts towards the goal.
Campbell: The Trickster's function is to disrupt.
Dramatica equivalent: The closest thing would be the Contagonist - the Contagonist's function is to deflect or hinder the efforts towards the goal. In addition and in opposition to the Guardian's function, the Contagonist represents temptation.
But this is where the similarities cease and Campbell's archetypes begin to break down in terms of their objective usefulness.
Threshold Guardian and Herald
Campbell: The Threshold Guardian's function is to test. The Herald's function is to warn and challenge.
Dramatica equivalent: There is no equivalent. Campbell sees both the Threshold Guardian and the Herald as characters responsible for driving the story forward. In the case of the TG, the hero must meet and overcome him in order to commit himself to his quest. In other words he turns Act 1 to Act 2. That's a lot of responsibility for one character. It's also extremely limiting creatively.
The concept of the Herald is even more egregious. This poor character has the major responsibility of issuing the "challenge" to the Main Character to embark on the journey in the first place. Proponents of Campbell's theory are quick to point out that this character can be a newspaper or a storm, but you really shouldn't have to bend a theory in order to make it work.
Act turns should not be tied to any one character. Not only is it limiting in terms of a writer's creativity, it doesn't even make sense. The development of a story's problem progresses along the competing throughlines (the main plot, the Main Character's throughline, etc.) based on the kind of drivers established at the beginning of a story's problems.
Logic and Emotion
The most interesting aspect of this whole study is the fact that Campbell is leaving out two very important archetypes - the Reason archetype and the Emotion archetype. Interestingly enough, most stories that follow the monomyth paradigm find a way to blend the elements of Reason and Emotion into the Hero or any one of the Allies attached to him or her.
The Usefulness of Any Archetype
Regardless of which paradigm is followed, stories that use Archetypal Characters often fall flat in the character department. Star Wars and Contact are not textbook examples of masterful character development. What you see is what you get. But what they can do is give an author a starting point or shorthand to get them rolling towards whatever it was that excited them about writing in the first place. I suspect George Lucas was more interested in battling light swords than he was the subtle intricacies of character motivation.
Clearly though, one approach is superior and far more succinct in its examination of what constitutes a complete story. Archetypal Characters, as defined by Dramatica, are seen as a collection of complimentary elements that work in tandem to provide an example of one way of solving the story's central problem. They are defined not by their relation to the Hero, but by their function within the story and thus, are not confined by one narrow view of what stands for a great story.