We've been revising our rate limits, and rate limits documentation, recently. The version live on the website doesn't mention any requests-per-second limits, but our last version did, and we're going to add them back in.
That aside, the change on 1 Nov was to start clamping down on how many requests per second each IP address can do. I've been adjusting that in production datacenter 2 all day to try and get a good balance -- because 100rps of new-nonce from one IP address is just abuse, for example, and that has to stop.
I'm looking at the 503 metrics out of staging right now and I need to spend some more time with the limits there, too. As an example, in Staging I've got /acme/new-acct set to no more than 1 new-acct per second per IP per load balancer -- and people are hitting it a lot. A lot more than Friday's numbers. Probably you are, too. I like that limit because we have no way to delete old accounts right now, but it's even tighter than we had documented of a limit of 20rps across new-order, new-acct and the other entrypoints.
Let me do some adjusting and I'll see if we can fix this for you. And we're going to keep iterating on the docs, too.