when you speak of sentiment, it is always tried and true measurables such as tick, trin, and put/call. What about Zeitgeist? Nine Eleven changed the world.
Interesting variation on "This time is different!"
I wish there was any set of indicators or regression equations that would be "try and true", I know of none. The only "seat of the pants" is the time variability (weighed toward more recent history, rather then multi year historical norms) of the correlation coefficients.