I am megacorp A. I just designed an ultra cheap to produce medicine against AIDS. Thanks to the patent I have on it, I can ask super high prices for it. Who cares that some dumb blacks in Africa can't afford it. I'll sue anyone who tries to produce it and make it available cheaper.
I am megacorp A. Due to some drug manufactures not having to pay any R&D costs, they are able to undercut us, and as such we won't bother put money into researching something that we can't profit on. Now there is no medicine against AIDS.
(I don't understand why you decided to use an example where the patented product already exists, considering how expensive R&D is)
It would be less of an issue if there was more public money put into public research, as then profitability isn't necessarily required for research to go ahead, but given the strong capitalistic leanings of America and other similar countries, this is a whole different issue.
(Yes though, this is patent law and not copyright law, which IIRC only has a 20 year protection)
or leave it up to the claimants and the legal system
IIRC not acting on a DCMA would leave them open for legal action too, so the only way for them to remove legal burden from themselves is to act on the takedown. claimants can take it to the legal system if they wish regardless.