In The Vision in Job 4 and Its Role in the Book by Ken Brown, Brown makes a great note about the relationship between synchronic and diachronic methodologies.
… the two dangers are parallel. Whether we focus only on the “original” form of the book and treat everything added or changed as relatively unimportant, or focus only on the “final” form of the book, ignoring whatever lies behind it, either way we prioritize a single point in its history to the exclusion of all others. Both approaches impoverish our understanding of the text in all its complexity (pg. 57).
He proceed by discussing how important it is to utilize a methodology that take into account synchronic and diachronic aspects of a book. In short, I appreciate his methodology because it, as he notes, allows the reader to observe and take seriously the various contexts in which the text(s) operated. There is no assumption that one redactor is superior to another. Additionally, more breadth of human experience and expression may be observed with this approach.
The Biblical Review 