Hi, welcome :)
I think all the channels have their own purpose... the only "duplication" is indeed the two forums.
I never used a wiki forum, but if we want to migrate from Ning to Wiki, we have to verify the possibility to:
- see a list of all the latest discussions: it's very helpful especially for people like us that go to the forum to try and address all questions
- receive a notification to thread one participated in: otherwise people have to go everyday and see if someone answered, and likely miss something
If the major concern is "not owning our own data", then moving the most possible out of Ning is the good solution. But also we have to consider that having a server to maintain, in the long run, it can become a tiring task, especially if the community grows and we start getting 20-30k page views per day. With Ning (or any other hosted server) this is transparent to us.
Simone