I have a use case where a subset of people are divided into exclusive buckets, and they each receive a particular type of email pertaining to that bucket. This would be a periodic activity, every week or so. 

These buckets are user-generated therefore they’ll vary every time, and APITB was the best way to go about it, having proven successful in most other use cases.
But the rate limit here is a huge bummer, as when I have a 100 buckets, I have to stagger these requests every 10 seconds for a really long time. I do not see how I’d use campaigns and segments here due to the dynamic nature of those buckets themselves, but perhaps I am missing something. 

Please advise on best way to go about on for this use case.