Scammers don't care about the DNC. Only law-abiding telemarketers respect it. You might want to invest in a call blocker or at the very least, don't answer calls from numbers you don't recognize and don't call numbers back "just to find out who called." If they don't leave a message, they aren't worth your time.
1) Consider blocking entire area codes, rather than individual numbers within an area code. Read your blocker documentation to learn how to do that.
2) Ask yourself why you are getting so many spam/scam calls. Many of us get only one or two spam calls a week. Are you posting your phone number in public places? Are you responding to questionable texts or calls?
The bad guys have several ways to get phone numbers. We cannot avoid the "war dialer" that may dial our numbers, but we can try to avoid making our numbers more desirable to the spammers, so they share our numbers among themselves. Think about it.
I just got my first call from this phone number today 5/2/2016 at 1:12. I did not answer and they hung up before my answering machine came on. Like you, I keep a list of the numbers, where they came from and date and time. I was even threatened by a call from NJ that said I have a criminal lawsuits against me. They have never called back. You can also get these types of calls from Florida stating you have a criminal lawsuits against you. She had an Indian accent and those who have complained all have the same case number.
I think the phone companies provide the robocallerservice for a penny per call. I invested in a call blocker but it died eithin a few months of purchase. My answering mach states "due to the violators of the do not call list we screen all calls, leave a messag and If we know you we will call you back " The only way they will stop is if there is no payoff to them calling. If enough people stopped answering unknown numbers we might discourage these scamming pests.