In my limited experience under the new regime, business class CASH fares tend to be lower over holiday periods (winter break included) while MILE fares tend to remain elevated. So you should perhaps consider looking at cash fares. That said, this seems more to be a case US-Europe than US-Asia so your mileage may vary.

You should also decide whether you are open to repositioning flights (and associated benefit/risks). Origin city matters a lot. You can get a $3,385 round trip one stop J fare on AA/JAL to SGN Dec 15 - Jan 5 if you depart out of LAX, for example. A similar flight (i.e. two stops since you have to consider the repositioning flight to LAX) is $1500 more if you depart out of Atlanta and that is on inferior carriers.