Katherine's death is when I thought that the show lost something (and I think that's when some of my flist quit the show as well), so it's certainly interesting to hear that ratings dropped by a lot at around that time!

But yeah I guess that TvD is still one of their shows that get the most buzz, plus Delena always seem to be storming fandom polls, so it's probably considered a success by the CW's standards still :P