Actually your numbers are pretty low
#blendercoders indeed has 187 , but those are the actual C coders working on the blender source (which I do not do), so its an equivalent of our phraro-dev, the equivalent of pharo-users is #blender with 360 members and the #blenderpython with 70 members which are people like me that work on blender addons using python (all these are online users of course)
BUT.... the blender community is enormous, its theorised since its impossible to know for sure that is around 1 million users, both professional and hobbists. As a result of this the community is highly fragmanted as all community of similar size are because they are impossible to be contained.
In Discord I am on 2 blender servers one has 175 online users and the other 75 online users. As such I have little reason anymore to use IRC and especially Slack (the only thing in Slack of interest to me is Pharo).