When Does Storytelling Overwhelm the Message?

My first graphic novel of the year was a biography:
I see the Promised Land: A Life of Martin Luther King written by Arthur Flowers and illustrated by Manu Chitrakar and Guglielmo Rossi
[Chennai], India : Tara Books c2010.

First, the good: The story blends oral storytelling tradition with the Patua scroll painting of India. If that sounds strange, I will say that the format takes some getting used to but is really an excellent use of the graphic novel format. I have little enough of an art background to comment on the illustrations, but the colors chosen and the use of white-on-black to quote from King's speeches or highlight a point is extremely well done.

The Questionable: The author, in using the African oral tradition, references "the Gods" and Martin Luther King Jr.'s "Fa" (a word I could not find a definition for, but given the context would call it "fate" or "destiny").

At first, I admit, I rather overlooked this. It bothered me, yes, but the narrator was also clear about King's Christian background and his family's long tradition of life in the Baptist ministry. I will also be the first to admit lack of knowledge about the 1960s, Martin Luther King, Jr. himself, and African storytelling tradition, so at first I felt unqualified to comment on this storytelling device. After a few people commented on my initial review on my LibraryThing talk thread, I started to think about this some more.

How much does a format give or take from a story? This is a question in any story in terms of first- or third-person narration, the inclusion of illustrations, or even the font. Is it readable? How wide are the margins? If there are multiple narrators, do each of these get a different font? When you're talking about a graphic novel, format is doubly important because you're including illustrations on every page and if done well, should blend and be as much a part of the story as the words. While I was reading I See the Promised Land, I really liked the inclusion and choice to highlight quotes from Martin Luther King Jr.'s famous speeches, and I thought it was an overall good introductory story to the topic. This overrode some of my reservations about the storytelling device of the (fictional) narrator's references to Gods, plural, and a "Fa," something I agree that Martin Luther King, Jr. would be appalled by. Now that's another thing - this narrator is fictional, is telling us the story of King's life, and could conceivably have a different point of view from King himself. I want to read more widely about King and the Civil Rights movement now to see if my initial impression stands.

I'm not sure I have an easy answer for "how much is too much." I do think that this element was an unnecessary layer that did not fit the topic - that is, a biography of a Christian man. Where would you draw the line?