This has happened to me but well before 10/14. I have 100s of terms with 100% bounce rate and I'm not surprised that those visitors are not sticking around. The bounce rates for my target keywords has remained the same but my overall bounce rate has increased from under 25% to 40%. It looks to me like Google is applying semantics based on the Monty Python Word Association Football sketch.
From time to time on Adwords I'll get a message *** keyword suggestions waiting for you. When I review them out of 600 or so there's often only one or two that are even worth considering. At least with Adwords I am in control but I'm wondering if Google (organic) is now applying the same broken word association games that Adwords uses with my content.
I strongly suspect that the issues that I'm facing post Panda are caused primarily by a lack of care in ensuring the UK English semantics rules are applied to UK sites. It looks to me like the semantics rules have been constructed by non-native UK English speakers. The same thing happened post Florida but it was possible then to get hold of GoogleGuy who quickly understood the issues and put it right. This time I think it is going to be more difficult.
One of the things I have done over the years is to make my main site semantically rich to remove some repetition and to give Google an indication of the broad field that I operate in and I think that this has helped me to rank well for the specific terms I am targeting. Now Google has lengthened the tail and applied dodgy semantics my current writing style may be counter production.