Sorry for the length, but I believe this is an interesting situation, so hopefully you'll enjoy thinking this one over a little. Thanks for taking the time!

Historical Information

• We’ve owned and operated printglobe.com since 2002.
• In late 2009, we acquired absorbentprinting.com and operated both sites until Mar, 2015, when absorbentprinting.com was redirected to printglobe.com.
• The reason we chose to redirect absorbentprinting.com to printglobe.com is that they were same industry, same pricing, and had a lot of product overlap, although they did have unique product and category descriptions. We saw a long and steady decline in organic traffic to absorbentprinting.com in the last couple of years leading up to the decision to redirect.
• By the way, while I understand the basics of SEO, neither I nor anyone else at our company could be considered an SEO practitioner.

Recent Information

• An SEO firm we used to be engaged with us reached back out to us and noted: “I started looking through your backlink and it looks like there has been a sharp increase of referring domains.”  They included a graph that does show a dramatic increase, starting around November, 2015.  It’s quite dramatic and appears anything but natural.  The contact from the SEO firm went on to say: “After doing a cursory review, it looks like a handful of these new links are the type we would recommend disavowing or removing.”
• We do little in the way of “link building” and we’re in a relatively boring industry, so we don’t naturally garner a lot of links.
• Our first thought was that we were the victim of a negative SEO attack.  However, upon spot checking a lot of the recent domains linking to us, I discovered that a large % of the links that had first shown up in AHREFS since November are links that were left as comments on forums, mostly in 2009/2010.  Since absorbentprinting.com was redirected to printglobe.com in Mar, 2015, I have no idea why they are just now beginning to show up as links to printglobe.com.

By the numbers, according to a recent download from AHREFS:

• Total # of backlinks to printglobe.com through mid-Feb, 2016: 8,679

• of backlinks “first seen” November, 2015 or later: 5,433

• Note that there were hundreds of links “first seen” in the months from Mar, 2015 to Oct, 2015, but the # “first seen” from November, 2015 to now has been 1,500 or greater each full month.
• Total # of linking domains through mid-Feb, 2016: 1,182

• of linking domains first seen November, 2015 or later: 850

• Also note that the links contain good anchor text distribution
• Finally, there was a backlink analysis done on absorbentprinting.com in April, 2013 by the same firm who pointed out the sharp increase in links.  At that time, it was determined that the backlink profile of absorbentprinting.com was normal, and did not require any actions to disavow links or otherwise clean up the backlinks.

My Questions:

• If you’ve gotten through all that, how important does it seem to disavow links now?
• How urgent?
• I’ve heard that disavowing links should be a rare undertaking. If this is so, what would you think of the idea of us disavowing everything or almost everything “first seen” Nov, 2015 and later?
• Is there a way to disavow at the linking domain level, rather than link-by-link to reduce the number of entries, or does it have to be done for each individual link?
• If we disavow around 5.5k links since Nov, 2015, what is the potential for doing more harm than good?
• If we’re seeing declining organic traffic in the past year on printglobe.com pretty much for the first time in the site’s history, can we attribute that to the links?
• Anything else you’d advise a guy who’s never disavowed a link before on this situation?

Thanks for any insights!

Rob