I had this same issue. A new Moen faucet in my bathroom and after a few months it started leaking from the tap. Rather than run out and get a new cartridge I attempted to see what may be causing the problem so I pulled off the cold water handle (which was leaking, hot water handle seemed fine) and using my hand I slowly turned the top of the cartridge and found that with a very slight adjustment the water stopped so I put the handle back on gently and screwed it back down while holding the handle to prevent it from moving. I'm telling everybody in the house to be gentle when turning the water on and off but my leak is fixed without replacing any parts.
I'm on a well so leaks are bad and I hope this helps some people.
Just a quick update on my tap situation. The leak was back again today and I thought for sure I was going to have to replace the cartridge but I'm trying to avoid it as the taps are only 2 months old.
I took the handle off and turned the tap 180 degrees and the leak stopped. My gut feeling is that there is something keeping it from sitting completely down but the handles were not touched as they were pre-assembled when purchased, I just sat the new faucet where the old one was after I used a razor blade to make sure the entire sink was clear of obstruction and then cleaned it. It's okay again but I'm sure I'll have to replace the cartridge but as I stated, the taps are only 2 months old and for what I paid it's hard to figure the cartridge is bad.
I also checked for hairline cracks and didn't see any in the brass. I do agree that plastic might be the better option so long as you're cautious as to how tight you go.