adder - 7:08 pm on Nov 17, 2013 (gmt 0)
A couple of questions:
Have you tried searching for your site using some of the keywords you know you ranked well for? Have your rankings really dropped? If yes, is there any pattern? What is affected - longtail or money terms?
What does Analytics say? Has any particular section of your site lost more traffic than other sections?
Have you checked GWT if there's a manual penalty notice?
Although occasionally deep crawl is an omen, there may be a completely innocent explanation for a deep crawl. Do you know if the bot struggled accessing any pages? Have you checked if Google has dropped any pages from its index?