One strategy tip: don't play cat and mouse. As you've demonstrated, if you change one thing, they will figure it out and change one thing. Not only does that not work, but you are training them that it's worth trying to beat your latest change.

Instead, plot a few different changes and throw them in all at once. Preferably in a way where they will have to solve all of the changes at the same time to figure out what happened and get things working again. Also, favor changes that are harder to detect. E.g., pure IP blocks are easier to detect than tarpitting and returning fake/corrupted content. The longer their feedback loops, the more likely it is that they'll just give up and go be a parasite somewhere else.