Last year's minor semifinalist was expected to be too strong for the Tactix in its last pre-season action before its opening ANZ Championship game against the West Coast Fever on Sunday.
But it was the visitors who were hungrier, and they fought their way to a well-earned seven-goal win.
Experienced centre and new Tactix captain Maree Bowden led from the front with some superb work in the midcourt.
Her combination with goal attack Anna Thompson was slick, and promising goal keep Charlotte Kight gave an athletic performance and disrupted the Steel's supply of ball.
Kight had an injury scare towards the end of the first quarter but returned to court for the final 15min period.
The Steel had its best period early in the match, shooting out to a 5-1 lead.
But the home side soon showed signs of fatigue from a busy pre-season campaign which has seen it play 19 games on both sides of the Tasman in the last five weeks.
"We have been training quite hard and the travel has been hard," Broughton said.
"But we shouldn't have been that tired. We were too loose on [defence] and we weren't looking after our loose ball. We weren't running as hard for the loose ball, so we need to tidy that up this week."
The Steel clung to a 16-15 lead at the first-quarter break but the Tactix had the better of the remainder of the match, winning the next three quarters 14-10, 12-11 and 17-14.
The Steel midcourt lacked its usual zip with classy wing attack Liana Barrett-Chase absent due to illness.
Steel skipper Megan Dehn donned the wing attack bib but looked out of place, and Wendy Frew had an off game, throwing away possession with some poorly directed passes.
The Steel also lost a lot of ball on the fringe of the shooting circle and lacked finesse and, at times, patience on attack.
"It was just a bad day at the office, really," Broughton said.
"They have to realise you can't afford to have off days. We really did not look after the turnover ball. We weren't patient enough."
Earlier in the day, the Steel had a 42-27 win over the Otago Lois Muir Challenge team.
