First of all, why do you take Luskin at his word? Spinning is his job.
Secondly, think about how Fitz does *his* job: he gets underlings to flip, and rat on their bosses. If he got Rove to cop a plea, it can only mean that Rove will spill the beans on somebody above him in the White House heirarchy, and there are very few people that answer to that description, and we would all love to see indictments handed down on them.
Fitz won a conviction against the governor of Illinois, but it took him years, and he had to make his case against a lot of lesser luminaries first. I believe that this is his modus operandi.
Think about the optics of United States v. Cheney, especially some time like October... that would be a Fitzmas to remember!