I think there are four distinct groups to blame for the drift in the plot structures, continuity and line errors from ACOS through to TOM.

1. First off I blame us - the fans. Specifically anyone who was part of the very visible stink kicked up about Perrin missing from TFOH and the screams of that times 3 when Mat was missing from TPOD. The grief RJ copped over those I've since felt is in large part responsible for the plot crawl from book 8 through to book 11.

2. So number 2 is RJ himself for not ignoring the fan angst.
The Perrin arc, the Egwene/White Tower arc, Rand arc and Elayne Arcs barely interact once Perrin leaves Rand, except for Rand and Elayne doing the deed and him taking Nynaeve with him. With hindsight the arcs would have been more tightly concluded if RJ had ignored the angst of fans missing from books and re-arranged these arcs from books 8 to 12. Perrin could easily have not been seen in TPOD, leaving more time for Elayne for example. The Elayne arc could have been pulled forward in place of Perrin to have her take the throne in COT. Then Perrin as a block after not being in 1 or 2 books. Similar moves could have been done with the Rand, Mat and Egwene arcs. And without having to do the one or two chapter 're-hashes' and filler chapters just to have characters on screen to placate fans I think we would have been essentially at the end of KOD after 11 books, not 12. We still wouldn't have had an RJ finished AMOL, but it'd be a hell of a lot further along - possibly even to the point where RJ could have split it in 2 and it ended where TOM does.

3. Brandon Sanderson - largely for the reasons outlined by DomA and Larry. I cut him some slack because he's inherited the 'every popular character MUST be seen every book' mantle. I can understand him not being able to get that overridden, even if it is even more obvious after TOM that given how the books were split, that Perrin didn't need to be and shouldn't have been in TGS at all.

4. 'Team Jordan'. Do they actually pay anyone to do continuity checks and editing? Because TGS was bad and TOM worse. Spelling checks I can cut some slack for in the rush to get a book out, but not continuity errors. In a series where allusions, minor character thoughts and interactions and obscure prophecies abound and are (to a certain POV) essential for taking in the complete story these more then anything are unforgivable. If it takes an extra month or three months to check the book to ensure it's 100% consistent within the WOT world, then this MUST be done. A book can be late only once, but bad forever. TGS and even more so TOM are unpolished stones. All the other flaws aside, the good parts of them are obscured by them.

The fact RJ wrote the very end of AMOL is the main thing that holds up hope that it MIGHT be the ending the series so deserves, but BS and Team Jordan are going to have to do a hell of lot more work on it. Most clearly at the point they've handed TGS and TOM to TOR. AMOL needs a LOT more time set aside for editing and continuity checking. Characters need to talk as they have the first 11 books, be in the right spot and act consistently with their personalities. I don't care if it means we don't see AMOL until 2013. I want it RIGHT, not as soon as possible.