I have a couple sites that have these, and I have done a lot of work to get them removed, but there seems to be very little if any benefit from doing this. In fact, sites were we have done nothing after these penalties seem to be doing better than ones where we have done link removal and the reconsideration request.
Google says "I_f you don’t control the links pointing to your site, no action is required on your part. From Google’s perspective, the links already won’t count in ranking. However, if possible, you may wish to remove any artificial links to your site and, if you’re able to get the artificial links removed, submit a reconsideration request__. If we determine that the links to your site are no longer in violation of our guidelines, we’ll revoke the manual action._"
I would guess a lot of people with this penalty don't even know they have it, and it sounds like leaving it alone really doesn't hurt your site.
If seems to me that just simply ignoring this and building better links and higher quality content should help improve your site rankings vs. worrying about trying to get all these links removed/disavowed.
What are your thoughts? Is it worth trying to get this manual action removed?

But they have been getting better every week since, just not back to where they were.