Our version was old - you were right. that was part of the issue, but it's thrown up a few interesting things for us.
We're getting somewhere with this now, so I thought I'd update. The reason that we're struggling is that we're trying to use scrapebox, a carpet bomber of a tool, to assist in some quite surgical work. The idea is that it helps us find quite a small number of very targeted, ranked blogs with follow comments. These will be part of a sustained manual commenting campaign rather than auto-post mayhem.
Bit strange maybe, but we're like that.
So, the problem with the DF plugin is that it just checks the page that it finds and most pages don't have comments. Very quickly large numbers of good blogs fall through the net as "unknown".
I've been trying to use custom footprints to find the post pages rather than the category or index and increasing the liklihood of finding posts with comments, so that there is actually something to check for follow status.
So, footprints including stuff like -"be first to comment" -"no comments" -"0 comments" etc.
Seems to be working out fairly well. Been getting 1-1.5% follows from that on the keyword sets we've tried so far. Other bonus is that it runs fairly quickly as the initial lists are smaller.
Could do with filtering out more category and home pages from the initial search, but it's getting there.