Prime example, /r/wtf. Comments constantly ridden with stupid discussions about what is WTF, and then, the post itself which ISNT WTF. The mods just dont do anything, and the subreddit just slowly rots. Then, all the truly WTF post are gore.
Using top comments and posts may be the answer, but then new and original content dies.
The horrible fact is that most people are happy to participate in this decline and just adjust to the new content. A lot of my friends say that they just go on Reddit and just upvote anything mildly amusinsg, even though they know its drivel. Because, well, its just the way reddit is going. Contact the mods, comment if something is awfull, screw hivemind. Hivemind doesnt portray all of reddit, just the select few teenagers and circlejerks who are willing to impose their views over the entire site.