I wouldn't be surprised if just delaying the server response by some 3 seconds will have the same effect on those scrapers as Anubis claims.
There is literally no point wasting 3 seconds of a computer's time and it's expensive wasting 3 seconds of a person's time. That is literally an anti-human filter.
"Anubis doesn't target crawlers which run JS (or those which use a headless browser, etc.) It's meant to block the low-effort crawlers that tend to make up large swaths of spam traffic. One can argue about the efficacy of this approach, but those higher-effort crawlers are out of scope for the project."
So its meant/preferred to block low effort crawlers which can still cause damage if you don't deal with them. a 3 second deterrent seems good in that regard. Maybe the 3 second deterrent can come as in rate limiting an ip? but they might use swath's of ip :/