Your Duke Biblical Textual Criticism is a pretty typical Modernist conclusion.
I'm not talking about the decision to call something an "Epilogue." It's very clear that, as in most Old Testament books, there are parts of Job that seem to be different kinds of text. Either a different style, or different vocabulary indicate such a difference.
But so what? The conclusion that it's less "true" is so full of hidden pre-suppositions that it's laughable. How, for example, should one determine whether the "epilogue" came last or first?
Or, perhaps the "writer" of Job is merely a kind of editor who's putting together stories he heard, under the guidance of the Holy Spirit?
Such a "revelation" by college professors and sophomores is only troublesome if one has a very weak view of the doctrine of inspiration. such a doctrine might look something like: the document is inspired only if one person wrote it and wrote it all in one sitting, preferably under some sort of hypnotic trance.
But a robust doctrine of inspiration can handle the fact that perhaps there was a rough draft of a letter first, or that there were source documents used by the author, or that someone came along later who knew the end of the story and added it on.
(The latter is quite obviously the case with Deuteronomy, where the accepted author, Moses, has his own death described. Of course, if you held something like the weak view of inspiration, you'd have to posit that God told Moses how he was going to die. But with a robust view of inspiration, one needn't do that backflip when you can simply take the step of saying, "Yep, someone else wrote that after Moses died, this person was also inspired to write that last chapter and to add it on to the end of Deuteronomy.")
A robust doctrine of inspiration must be able to account for multiple source documents, multiple authors, multiple contexts, multiple audiences, as well as the transmission of said documents and the concilliar decisions to finally decide which books & letters counted as inspired and which ones were heretical.