I do some work with a Bible search site that saw its traffic drop dramatically right around the time that Google implemented some of these changes. My conjecture is that the site was penalized because it had similar content (the Bible itself) as other sites.
Pages crawled is a strange graph to post. The dramatic dropoff makes me think you have a crawling problem, not that google pegged u a content farm. Is google simply not crawling content farms? No they are ranking them lower but still crawling them.
I agree with this. I have had many sites deindexed due to being thin affiliate sites using the same affiliate feeds that tons of other sites use. They still get crawled. Also, I have had sites go through a huge drop off in bot activity and still keep whatever rankings those sites had. Bot activity is cyclical. I don't think you can make a direct correlation between bot activity and ranking.