No, you could do it on a case-by-case basis at the sub domain level. (At least that's what I would do)
Discussion
You can do one Tor domain with 200,000 pre-generates keys or split them into a few hundred domains. Or just use IP directly.
So we would filter the one Tor domain? Directly using IP is a problem for the spammer moreso than it is the network.
Maybe I’m missing something here but you’ve not explained why this wouldn’t work, you’ve just given more things that I’d want to filter out.

