@edge (or others with same problem regarding specific pages being routinely hit) have you just changed the filename, modified top down internal links to that page and NOT 301'd? Just accept the 404 with no worries.
Reason I ask, back in 2003 or 2004 I had something like this happen to one of my sites and that's what I did. The search engines found the pages again, ended up in serps, but the bad actors didn't follow the change, ie. they disappeared.
Might be worth trying, after all, the value of these pages is currently kaput. I'd rather have a week or so wait to be rediscovered than to get hammered.
Also, what referers (sic) are attached to the hits? Anything there?