“If there's a high pass rate in a quarter, is one probable reason that the test was easier that quarter?”
A lot of it has to do with business cycles. Q1 generally has the worst scores of the year. It's generally believed to be due to the heavy workloads experienced by tax & audit at that time of year.
“Because I did amazing in FAR, even though I shouldn't have (crammed for it).”
It's possible. I missed FAR by two points without studying at all (took it the day after AUD and was working 50+ hrs a week at the time). Also, I'm almost four years out of school and haven't done a debit or credit since I graduated. Sometimes you can get lucky and get a SIM or two that you really nail (that's what happened to me). Conversely, you can get unlucky and hit hard on stuff you don't know as well. I've been referring to my retake as “the FARpocalypse”.