Tickford's lead driver was also its only race winner this year, a sublime drive on the Gold Coast one of very few highlights in what was a tough year for the four-car Ford squad.
Despite a highly-rated driver roster, Mostert was also the only Tickford pilot to land in the Top 10 of the overall standings. He ended the season sixth, while former series champ Mark Winterbottom languished in 12th, Cam Waters just 16th, and much-hyped rookie Richie Stanaway 25th.
While the shift to the Mustang bodyshape for 2019 has provided a ray of optimism for Blue Oval fans, Mostert warns that changing panels won't guarantee a change in fortune for Tickford.
With Scott McLaughlin having sealed the title with the ageing Falcon FG-X aero, Mostert says there's more to Tickford's struggles than downforce.
"The aero from the FG-X to the Mustang isn't the thing we were waiting or looking for," he told Motorsport.com.
"There are still a lot of big fundamental things that we need to do better. It's about moving forward. The guys down pitlane aren't going into next year with the same stuff, they're looking at making things better and faster.
"For ourselves, we've got to try and work on our massive weaknesses that we had this year and come into next year faster and stronger."
Moving forward will be key mantra at Tickford over the off-season, with Mostert identifying a lack of progress as the team's major issues this year.
He admits the team was "blindsided" by improvements made by other teams on the grid, and it wasn't until his win on the Gold Coast and podium in New Zealand that he started to sense real progress in his own garage.
"It was a tough year really for the whole team. We were a bit blindsided by our performance at the start of the year," he said.
"You've got to look at the championship as a whole and see how strong some people got from their off-season into the following year. It's not like we got it wrong, we just got left behind, if that makes sense.
"The things that used to work we were doing on par [to 2017], but the competition stepped up. That was the biggest thing.
"The engineers had to get their innovative caps back on, the drivers had to learn how to drive the cars a bit differently again to extract the speed from them, and as a team effort it was a long year to the point where we started to make a little bit of progress."
Tickford has been provided the basic panels for its first completed Mustang, with the aero-dependant parts to follow in the wake of the ongoing official aero testing.
The team will field four Mustangs next season, with Mostert and Waters locked in, and Will Davison set to join the fold in a new technical tie-up with 23Red Racing.
It's yet to be confirmed whether Stanaway will stay with the team for a second season, with Lee Holdsworth and Jack Le Brocq having been linked to his seat should there be a parting of ways.