Depends on if you want to promote better discussion of what is on the blog. If it is setup well, it will be easier to get comments on what is on the blog, by having an organized section on a forum.
It really depends. I think in most cases, a forum might detract from your blog unless carried out really well. If you have a decent visitor base, a forum could help bring them closer though. It could also do the opposite and spread your base out to far. I’d assess what you want to accomplish and determine how a blog would fit into your structure/time.
I have seen blogs post and that members get redirected to the thread for that blog. But I see no point in that and rather post a comment on the blog post