Well, starting of with 10 the first 4 months, then going to 20 and later 40 didnt help Blizzards cause at all (specially when they didnt give a clear statement about 60 raids until very late).
People are expected to double their roster as the game is dying, or run 40-man guilds with 10 man content for half a year …
If it was 40-man from start atleast people would have a chance to prepare for it and keep players busy, but then again I doubt SoD would have had half its population at launch if that was the case.
This post sums it up pretty good (long as a book however): 20-man raids as standard going forward