But there was also a significant silver lining on Sunday for the second-placed Australian, who grabbed a spot in the 2026 British Open at Royal Birkdale.
DP World Tour star Hillier started the final day with a one-shot lead over countryman Kerry Mountcastle and Australian Curtis Luck and was never headed.
The 27-year-old had five birdies and just the one bogey in a hugely-impressive final round of four-under 67 to top the leaderboard at 22 under on a cold day with intermittent rain at MiIlbrook Resort.
"I knew there would be some guys challenging me today," said Hillier, who continued his hot start to 2026 which also includes two top-five finishes on the DP World Tour.
"Herby is obviously a class player and I saw him up there towards the end and knew I had to keep my head down.
"The blood was pumping, the adrenaline was going.
"I'm really proud with how I stuck with it."
Since Mahal Pearce's win way back in 2003, the only other Kiwi golfer to lift the NZ Open trophy aloft was Michael Hendry in 2017.
"I think this is going to be the best eight days of my life forever," said Hillier, who got married last Sunday.
"The wedding was the best day of my life, absolutely, and this is the best day of my life on the golf course.
"It's pretty awesome that it's happened in such a short period of time."
As Hillier was already locked in for the British Open, the spot for the highest-finishing non-exempt player went to LIV Tour player Herbert.
The 31-year-old has teed it up in 17 majors - with a best finish of a tie for 13th at the 2022 US PGA - but has only qualified for two of the last eight.
"I'm really looking forward to it," said Herbert.
"My game has progressed a lot with the opportunities I've had out there on LIV.
"I've been able to learn off the other boys and our off-season allows us not to just tune up every week to play, but to actually work on your game, do a lot of development on your game."
Good mates Hillier and Herbert both shot rock-solid 67s on Sunday, just a single shot off the low round of the day in difficult conditions.
It completed an impressive comeback in a tournament which the Australian started ignominiously by dropping three shots in his first three holes in dreadful conditions back on Thursday.
"There were Sunday pins out there that were tricky to get at, so you had to be patient," said Herbert.
"It was one of those days where four under was a very good score."
Japan's Tomoya Ikemura (67) and Mountcastle (71) tied for third at 17 under, while Australian Travis Smyth finished strongly with a 68 to improve to outright fifth at 16 under.
Luck's title bid unravelled at the par-4 sixth hole when he lost his ball after hitting his tee shot way right and then had to settle for a double bogey.
The West Australian limped home with a final round of eight-over 79 to slip all the way down the leaderboard to a tie for 23rd.
