I wasn’t ready to tackle the whole mess, but you are correct, the issue pervades all of the places you mentioned, plus here, man pages, bug tracking, mailing lists and many, many more. Being varied is not necessarily a bad thing, its the not having a propagation process and the staff to do it that is a bad thing.
When a bug is closed, it should be reviewed to see if it needs to be documented in the primary documentation, but thats not done.
When a mailing list discussion or forums discussion ends, it should be reviewed to see if it needs to be documented in the primary documentation, but thats not done.
And so on.
For example, a discussion on a mailing list or forums should lead to an entry on wiki and sometimes an article on ask. If deemed appropriate, that should then be fleshed out to a proper and official article on help. Help should then lead to server/desktop guides.
Parts of that are great community projects. Forums and wiki specifically. But other parts don’t lend themselves well to being volunteer efforts. Its not hard to get people to write a new article. its almost impossible to get volunteers to keep them updated over the long haul.
The SmallBusinessServer is at https://help.ubuntu.com/community/SmallBusinessServer. Its a set of tutorials with a specific use model in mind. When complete (and unfortunately, paid work needs to happen before I spend any more time on that project), this set of tutorials makes Ubuntu much more accessible to any anyone running a small business.