I was always disappointed that the series basically climaxes in 4X06 and that everything is basically an aftermath of that. I know that JMS wanted to show the beginning, middle, and aftermath of a war, but it's not dramatically satisfying.
Of course it's subjective, but I prefer it the way it is. Remember that the story isn't about the Shadow War, or the Narn-Centauri War, or Earth Alliance Civil War. It's about a place and the people who lived and worked there against the *backdrop* of a brief maelstrom of history. Because of this, I don't believe it would have worked better if the climax had been the way you propose.
For one thing, dealing with Earth before the Shadows is just plain odd since Earth was essentially as much in the Shadow's pocket as was Centauri Prime. Also, it'd make no sense for the AoL to take time out from countering an all out assault on the League worlds to sort out one mostly insular rogue state--yeah, in this war, Earth was North Korea.
Another problem is that the set-up wouldn't work as well either. Placing 'Severed Dreams' a full season earlier would dramatically truncate the slow creep of a totalitarian regime, which was a major theme of the show.
For my money, the only real weakness of the show's overall pacing is down to the show makers having to adapt on the fly to external events--the slight compression of the civil war arc when they thought the show was cancelled, Claudia Christian's unexpected departure and the loss of the original season 5 notes all conspired to throw things off.
Short answer: IMO a better order would have been the one initially intended.
I extend the Shadow War so that it's not prematurely condensed because JMS thought the show was getting cancelled. More space for active conflict with the Vorlons and the Shadows, more time to learn more about Lorien and the First Ones.
As far as I'm aware, the Shadow War wasn't compressed at all, it was all in the latter half with the Earth and Minbari civil wars. Indeed I think the season finale would have been 'Intersections in Real Time', so we're only talking three or four extra episodes.