As all the main points have been made, I'm gonna hijack this a bit (but still related)

Over the past 3 days, I tracked arena activity in terms of kills/time. This chart shows kills per hour. In (Euro) mornings, combat AH almost comes to a halt (still the odd base changing hands, though). On Wednesday, there was a period of two hours, when not a single kill was made.

I will try to dig up some older data, to see if the relation of kills between Euro prime and US prime has changed over the past 15 years or so.