You may find the sibling topic Human-driven copy-paste spam informative if you’re not following it yet.
This form of spam only works because it’s invisible to moderators and the active community. That’s the only reason it’s happening. Perhaps all edits could bump the thread in the latest activity view — if the topic has already been read, then it’d be a direct link to that edited post. That would completely solve both issues (the spam and the worthless initial copy-paste content) in one fell swoop.
Even simpler (although not quite as effective), I know my fellow moderators and I would happily keep tabs on a special view that simply displayed posts that have been edited, sorted by their edit time (and perhaps optionally restricted by trust level).