The cookie will be invalidated if shared between IPs, and it's my understanding that most Anubis deployments are paired with per-IP rate limits, which should reduce the amount of overall volume by limiting how many independent requests can be made at any given time.

That being said, I agree with you that there are ways around this for a dedicated adversary, and that it's unlikely to be a long-term solution as-is. My hope is that the act of having to circumvent Anubis at scale will prompt some introspection (do you really need to be rescraping every website constantly?), but that's hopeful thinking.