"All week we've been playing an aggressive style of play and couple of times we've had to get ourselves out of tricky situations," international midfielder Muir said after the match.
"Having trust in our game plan that we can score goals at any time in the game really paid dividends in the end."
The NHL format was changed this year. Instead of a full round robin of seven games before knockouts, teams were grouped in pools of four to mimic international play, followed by quarters, semis and finals.
"I really enjoyed it," Muir said.
"In the past it has been a really gruelling tournament and by the last couple of games you were stuffed. The quality in last couple of games this year really showed the format was a positive change."
Capital won the bronze, with a 6-1 flogging of Southern, Benedict van Woerkom and Dane Lett scoring two apiece, while defending champions Midlands finished fifth.
Northland's men have issues. They conceded 21 goals and scored none in their last two matches, today's being an 11-0 pounding from Canterbury, for whom Sam Lane scored six times. Inevitably Lane finished top men's scorer at the tournament with 13.
Midlands bagged their first K Cup women's title since 2013 with a convincing 4-2 win. The result was a reversal of the opening pool game between the teams, won 3-2 by Northland.
All six goals in the game came from Black Sticks players.
Midlands had taken a commanding 3-0 lead by halftime with goals from Gemma McCaw, Rose Keddell and Sam Charlton.
Stacey Michelsen gave Northland a boost with a goal a minute after the third quarter began, but Shiloh Gloyn scored a fourth for Midlands two minutes later. Ella Gunson's goal 17 minutes from the end was small consolation for Northland.
McCaw, nee Flynn, who took a break from international hockey this year, was a significant factor in Midlands' success, scoring in five of their six games.
Auckland took bronze winning a shootout against North Harbour 3-0 after the match finished 1-1.
Defending champions Canterbury finished a disappointing sixth.
Northland's Jodie Nicholl and Canterbury's Rachel McCann finished joint top K Cup goalscorers with six.
Gunson and Auckland's men's skipper Arun Panchia won the tournment MVP awards.
New Zealand's squads for the Oceania Cup, to be played in Sydney in mid-October, are expected to be name early this week.