The Welsh hosts scored all their points in the first half via a Luc Jones try and a conversion and three penalties by fly-half Jason Tovey.
But the Saints outmuscled them up front, running in five tries including two from a lineout out with a third also coming through a penalty try after winning the scrumming battle.
The Dragons are yet to settle on a tight five, having used 19 different combinations in 21 games so far this season and naming an unchanged quintet just once in consecutive RaboDirect PRO12 games last November.
And Jones, whose forwards coach Kingsley Jones is currently away with Russia ahead of World Cup qualifiers and the European Nations Cup, knows they need to address their current weakness,
"Our front five had a tough time against Northampton," Jones told the South Wales Argus. "The challenge for me as director of rugby is to ensure the expertise comes into the region to enhance our ability to scrum and maul.
"Northampton are a top four side in the Aviva Premiership and a genuine power side.
"We need to improve in that department; there are some glimpses of improvement but in tight play it only takes one forward to not do their role and it all falls down.
"There are lots of ways to improve tight five play and the expertise in Wales isn't great, either on the field or of it. We need to provide a platform in order to be successful in the future."
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