Revulva made a comment, but it's later in this thread, so I'll post an update here too (sorry for the repeat)!

We got locked out of the armory! Grr. We only send 2 requests per character (instead of over 50 for every item, gem, etc), AND we throttle the number of requests sent to the armory at a time. Even with those restrictions, we still got banned.

Blizzard doesn't tell you where you need to be to be complaint, likely to make sure people don't find loopholes in the system. If a spammer knows they get killed at 1,000 requests per hour, for example, all spammers would throttle to 999. Unfortunately to protect against spammers, we get hurt. I'm trying to reach out to them to whitelist us... if anyone has a contact, reach out to us with a PM on our forums.

Last time we had a traffic spike, about a year ago, we were locked out for 24 hours. We hope it's shorter, but at least not longer. I'm very sorry about this... Mr. Robot just wants to be friends... he really doesn't hate you like the message says ;)