Q:

Rhetoric: How to frame redundancy in an argument as deficiency?

How can we categorize redundancy in an argument as deficiency? That is, weaken the argument because of its redundancy? 
Suppose X is an argument that boasts coherence and clarity, but it has various passages that are redundant. 
Also, keep in mind I am not trying to weaken the argument from a logical point of view but more of a rhetorical point of view. I would also appreciate if you could cite any literature that cites redundancy as weakness of a work.

Edit
by "not trying to weaken from a logical point of view" i mean I am not looking for a flaw in the argument's logical structure as far as deduction or induction is concerned. I am looking as to how can we weaken the argument solely because it has redundancy. 

A:

There has been an emerging literature within the field of logic and computer science engaged with solving the problems encountered in the reasoning area of artificial intelligence which has consequently led to the construction and presentation of new 'computational models of argumentation' which contains material pertaining to the role of redundancy in argumentation!
For instance, at the Third Conference on Computational Models of Argument, held on September 2010, there was a paper presented by Phan Minh Dung & Francesca Toni, titled, 'Some Design Guidelines for Practical Argumentation Systems' [now published in the book, titled, "Computational Models of Argument: Proceedings of COMMA 2010" edited by Pietro Baroni, F. Cerutti] whose abstract reads:

We give some design guidelines for argumentation systems. These
  guidelines are meant to indicate essential features of argumentation
  when used to support “practical reasoning”. We express the guidelines
  in terms of postulates. We use a notion of redundancy to provide a
  formal counterpart of these postulates. We study the satisfaction of
  these postulates in two existing argumentation frameworks:
  assumption-based argumentation and argumentation in classical logic.

Within their article there is a section, titled, Postulate 2.2 (Relevance), which takes into consideration redundancy and states the following:

Intuitively, this postulate amounts to forcing proponents and
  opponents of arguments to focus and avoid digression not contributing
  to the important points they want to make and possibly opening-up
  attacks from their counterparts . . . . this postulate can be
  interpreted to mean that the support should be necessary to establish
  the claim, in the sense that the removal of any part of this support
  would render the arguments illegitimate. In a weaker sense, this can
  be interpreted to mean that the argument is a defeasible proof of its
  claim from its support, without any obvious redundancy of any parts of
  the support.

This short excerpt highlights one possible disadvantage in employing redundancy in an argument, namely: not advancing the contention further. Alongside this possible disadvantage, there could be an issue with redundancy with how an argument is presented: if there exists irrelevant material which can be removed without loss of information, then that material ought not be kept. 
However, Laurence R. Horn in his paper 'Almost et al: Scalar Adverbs Revisted' from the book, titled, "Contrastiveness in Information Structure, Alternatives and Scalar Implicatures" edited by Chungmin Lee & Ferenc Kiefer claims the following:

"[A]s shown in Horn (1991) and contra Sadock (1978), informationally
  redundant propositions can be asserted as long as they introduce a
  rhetorical opposition (Anscombre and Ducrot 1983), typically signaled
  as above by but. Thus, where the but clause is semantically
  entailed / presupposed yet felicitously assertable:
a. I don't know why I love you, but I do.
b. Obama barely won the nomination, but he did win.
c. It's odd that dogs eat cheese, but (eat cheese) they do.
d. I'm sorry I said it, but (say it) I did."

Here Horn presents examples where redundancy can, in fact, inform an audience by introducing rhetorical opposition. These statements can introduce meaningful information by re-affirming what has already been said.
There's also Austin J. Freeley and David L. Steinberg's book, titled, "Argumentation and Debate: Critical Thinking for Reasoning Decision Making" which affirms the usefulness of redundancy claiming:

Repetition and redundancy are often frowned on in writing,and authors
  are urged to steer clear of them. For the speaker, however,
  judicious repetition is essential to both clarity and emphasis. If
  listeners miss a critical word or phrase that is uttered only once, the
  speaker’s case may never be clear to them. Listeners cannot turn back
  the page to reread something they missed the first time.

Relevant Resources:
1. Informational Redundancy and Resource Bounds in Dialogue by Marilyn A. Walker
2. It’s Not Always Redundant To Assert What can be Presupposed by Yasutada Sudo
3. Argumentation and Debate: Critical Thinking for Reasoning Decision Making
4. Some Design Guidelines for Practical Argumentation Systems by Phan Minh Dung & Francesca Toni

