Your comment drew my attention to the letter - it is understandable and relatively free of the bureaucratic B.S.
I predict that simply as a function of attempting to save face, the press will continue to ignore the simple fact that Comey usurped the role of prosecutor; and by agreement, nobody in the prosecutor's office voiced an objection.
Rosenstein's letter will be buried under an avalanche of meaningless speculation and illogical criticism (for example, "timing" or "to stifle the Russia investigation").