At the moment we've got 62 questions tagged with [discussion] on meta. I believe that this tag is insignificant and should be avoided if not even removed.
The main purpose of the meta site is discussion, so that tag is not very differentiating.
I can see some discussion-only tagged questions regarding community wiki, badges, comments, questioning, answering, quality, FAQ or SO. They're hard to find if I look for the subject as long as they don't get the subject as tag but remain merged to discussion only.
Questions with just a single tag [discussion] should get a tag describing the topic of the discussion, at least if it's not too uncommon.
Though I can see that [discussion] is marked as required tag. Perhaps this might be changed technically.