Well, it's an overall issue with their music really, that they're all in a continuous turf war. JP wants a thick, full-spectrum sound, and JR loves playing both hands. So, they're constantly encroaching on each other's sonic turf, with JM often being the loser of the battle. It also doesn't help that almost everybody plays at any given time. It is my theory that FII sounds so good because Kevin Shirley cut through the tracks with a machete, freeing up that sonic space the instruments needed. MP hated it because it cut away material, but it's what made it sound so good.
I kinda get what you say, but I don't thing that the arrangement and song structure per se (which is the element that was changed the most in FII) had much to do with the album's mixing process. Now, that being said, I think that Shirely's producing helm enabled him to call some important shots in the mixing process like saying: Hey, during this part of the song we should let the keyboards breathe and have the vocals and the guitars come upfront. That's an approach that has been missing ever since SFAM (as much as people, including me, love the album). Everything sounds loud, proud and with arse & balls. Even the 'ballads'.
It's been mentioned a lot in the forum that DT have been in need of an outside producer for quite some time now, and although to some extent I agree I get why they don't want to; because they really don't need
one. Their music is still being very well-received, and given the size and budget of a tour like 'The Astonishing' their also not suffering in the financial department, so even though there's a vocal minority like us that love to discuss every little gimmick they won't get any outsider anytime soon. Also, we're talking about a band that has a total of 13 studio albums and a shitload of extra material in their discography, from which only 4 of those albums were produced by someone not in the band. It wouldn't make sense for them to go back and look for a David Prater