I was close. They are on top of the second worse, after the NFC South, where literally every team had a losing season.
Well, depends on how one looks at it.
The NFC South finished with a combined record of 30-38.
The AFC North finished with a combined record of 29-39.
The NFC East finished with a combined record of 27-40-1.
True. I was looking at it from the perspective of the weakest winner of a division, but maybe not the weakest division overall.
Though by your measure that still puts the AFC North as the second weakest. 
Well, good point!
To the surprise of nobody, the NFC West is the strongest by this metric, with a record of 41-27, which includes the Cardinals at 3-14. NFC North isn’t far behind, with a record of 38-29-1. That’s the only division with all four teams above .500.