I honestly love seeing this because it somewhat upsets me to see, I know weird... But Google's John Mueller responded to a webmaster in a Google Webmaster Help thread about him losing 90% of his "indexing" after the Panda 4 .0 update. He said, 15 years of work now "down the toilet."
John Mueller said nope, "you're sites are ranking where they'd normally rank." I scratched my head and said, do they? And looking at SearchMetrics, it doesn't seem Panda 4.0 hit it recently at all:
Of course, this makes me go back to me wanting Google to add an automated action viewer or the like to Google Webmaster Tools.
John told this webmaster that the "door is open" and he can do wonders with his site. John wrote:
Your sites are ranking where they'd normally rank -- there's no specific algorithm that's treating them in any special way at the moment. So in short, the door's open. That said, things always change in search, be it our algorithms, what users expect, or what other sites are doing. It's normal to see fluctuations over time. My recommendation would be to look at your sites overall and think about what you could do to significantly improve them. Maybe it makes sense to fold them all into a single site, so that it's easier to focus & implement changes? With a handful of sites, that's essentially up to you (personally I'd try to keep things simple and put everything into a single one, if these were my sites).
I just don't get hope people just claim things without even consulting anyone about this. Step one, see what is impacting your web site and tackle it from there.
Forum discussion at Google Webmaster Help.