If bursts are your issue, implement a message queue.
Whispers are not designed for this sort of purpose, so if you’re trying to force a solution together using it then you’ll run into the limitations of the Whisper system. Rather than open up the whisper system for potential abuse by expanding rate lmiits, and having to have the devs apply for and wait for rate limit increases, it makes sense to use/develop a solution that’s more fit for purpose as many of the larger streams/events or even small streamers with structured moderation teams already do.