It would definitely help to have the developers in there. In Particle's case however, the devs would most likely not join that channel, to keep noise to a minimum and stay focused. In general, those with the most answers are right here on the forums. An added benefit is that it serves as an archive that can be searched through. Working with Slack I've noticed many raised topics quickly vanishing under a flood of other chatter.
As for bugs, Github is probably the best place to raise them, since the Devs use that to work on.
More pressing issues like:"the cloud seems to be down" usually get picked up really quickly when posted here on the forums. The 'elites' have direct contact with Particle, and we definitely raise some flags when things seem off, coming from the community.
While I'm not opposed to additional platform, I worry it might spread the knowledge, and community, rather than keeping it centralized and easy to find. The forums have worked really well for Particle over the years, so I'm not quite seeing the value-add from 'splitting' that up yet.
We've have a Slack channel for the community (invite based, around 100+ of the active community members), which barely got used, with the last post being over a year old. Not sure if it would be much different if opened up to a free-for-all.