Is there a conflict between coherence & power and fragmentation & incompleteness?
To answer this question, we must look at the correlation between the two ideas. Coherence & Power, as a rule, would refer to the ability of a clearly stated idea to have power over those hearing it; if your idea is clear and simple, there are fewer gaps to work in for criticism. In this case, for an idea to have real Power, it must be Coherent.
Fragmentation & Incompleteness, while not referencing power as such, would still be a weaker example of the idea; when you cannot marshal your thoughts in a form that is easily understandable, listeners will raise questions and doubts; as well, if your idea is incomplete -- if you have not considered all the possibilities -- there will be room for attack.
Therefore, the conflict would seem to be more along the lines of Clarity & Objectivity rather than Power, which itself will come with the ability to present your ideas. To be Clear about your idea, and then Objective about all factors and consequences, would be to present a Coherent thought; those operating on Subjectivity, or Emotion instead of Reason, would not be able to present an idea in a convincing manner. Instead, the Subjective idea would only appeal to those who also have Incomplete ideas, and so would not be disseminated in a Coherent form.