It's not a bad idea to create channels for incidents. Ever tried to keep an incident timeline in a Jira ticket? It's absolutely horrendous. We used to automatically create a slack channel whenever a Jira incident ticket was created, and post it into the engineering channel with a message like "SEV1 incident, please join channel #INCIDENT-21". Slack is real nice for posting graphs, links, screenshots, going off on different investigation threads, pinning a status that gets constantly updated, calling out for people to join the channel using @you-hoo and running automations using bots. Jira absolutely sucks for live incident handling.

Of course, you still wouldn't have 8500 channels. That's a lot of incidents.