[bodyfour]

I think the LSB bits of arrival time is actually a really good distribution long-term (remember: we want the distribution to be uneven in the short term, but even in the long term) Maybe you could improve it a little bit by making each bin a prime number of seconds so automated messages sent at the same time every day can hit each bucket eventually. i.e. instead of 8 second granularity, use 7 or 11.