Hi,
I tried not allowing exit connections to IPs assigned by ARIN [...] but it didn't seem to help much at reducing DMCA complaints.
That's not what I tried to say. I had a 50mbit/s exit node IN Holland with open exit policy and never once received any complaints, because the DMCA hunt for "source IPs" is happening country based. But now that you say they still deliver their spam to countries where they just don't have any lawful basis to do it whatsoever, I think my ISP just filtered them (and that's what any Non-DMCA-Country ISP should do).
In Germany, a similar law is in place, but there still seem to be a lot less companies doing automated scans of tracker IP connections. Olaf with his German node said he receives only single complaints every once in a while, and not massive DMCA spam.
I would also scrape trackers for connecting IPs, then run them through a country IP filter, but they seem to be doing more checks than that: In my case (and a lot of exit traffic) DMCA complaints stopped completely after I changed exit policy and blocked random ports (while I do still allow port 80 connections, and that includes trackers).
Moritz