Last year the Delta sale seemed to peak the Mon/Tues/Wed of Thanksgiving week with not seen before pricing $400-500 RT even to minor cities like Montpellier or Marseille, although major city nonstops like London and Paris were a bit higher. Note that for me the cheap Delta fares were only available on klm.com, not Delta.com, and not valid for summer travel.
I wouldn't plan on this happening again since pricing seems higher this year.
Also of interest to me was that discount airlines did not match fares during this big sale or stray from their usual pricing scheme.
Because I am fixed to set dates/locations I have already purchased my summer tickets, Delta miles there, Icelandair cash + points return, $330 each person RT so not bad.
Open jaw pricing is cheaper because it means no backtracking and no extra nights staging in hotels to provide time cushion for separate tickets, etc.
You could look at double credit card bonus for AA points, Citibank and Barclays AA cards would separately net enough AA points for two one ways, but be careful since transatlantic on BA with AA points is no deal, the fees are almost as high as a regular ticket, must be AA or FinnAir plane over Atlantic, then BA onward from London OK.