Although it may not be Panda, this wouldn't be the reason to dismiss it: "many detailed top-ranking pages with unique content are suffering alongside everything else"
That's actually a big part of Panda, as Panda happily destroys good pages simply because bad pages are effecting the entire site. (And of course, I'm not making any judgments by using the terms good and bad - just using those as quality designations assigned by Panda, not me). That's the one piece of Panda that Google has been pretty clear on - some bad pages can bring down the whole site.
So, although Panda may not be involved, don't dismiss it simply because the great pages are suffering as well.