I see @ mention abusers as a different breed because for the most part their Tweets are not technically duplicates. They are complete pollution for sure and harder for an individual user to stop preemptively. At least if someone is annoyed with recurring or duplicate tweets they can simply unfollow that account and there's a self regulating mechanism. Ultimately the real pollution issue is the @ mention system itself, not recurring Tweets on individual accounts.
If Twitter wants to clean up the pollution, as they put in their message to Dewald, they would have a lot easier time rooting out @ mention spammers than trying to figure out some pattern of recurring Tweets looking back into history. You can usually determine an @mention spammer by looking at the first 5-10 Tweets and simply counting the @ symbols. The DM system is already polluted beyond hope. @ mentions are right on the heels of being useless to businesses trying to track the brand. In the grand scheme of Twitter problems, it seems to me that recurring Tweets are way down on the list and I think they're pulling a real tool out of the grasp of many businesses, enough that I don't know whether I can honestly suggest a business spend time on Twitter.