But the defence coach, who joined the club in January 2020, knows the team must now reach a new level if they are to be top-four contenders this season.
Saints are currently fifth in the Gallagher Premiership, having won four of their seven league matches so far this season.
But they are ninth in the standings when it comes to points conceded, with their total of 186 being bloated by the concession of 55 to Leicester Tigers last month.
Saints have shipped 121 points across their past three matches in all competitions, including 15 tries.
But Vass feels the team is making improvements, particularly in how they defend under pressure inside their own 22.
He said: "It (defensive security) comes over a period of time, it doesn't change overnight and sometimes not even over the course of the season.
"We have improved immensely in that area of the field, defending in our 22.
"Still, if you give good teams too many opportunities to have a crack in your 22, eventually they will score.
"A lot of it is allied to how you defend in the middle of the field because that's how people enter your 22.
"It's really about defending well the whole length of the field to stop people getting in those scoring zones."
Reflecting on the season so far, Vass said: "Once the international games come and the squad is more disrupted it becomes harder to be consistent.
"We've played a good game, a bad game and a medium sort of game so in those periods we have to strive to be more consistent when we haven't got a full group to pick from.
"We're fifth in the league and that's about right for where we've started the season."
But Saints are well aware that they must get back on track soon, following defeats to Leicester, Sale Sharks and London Irish.
Vass said: "It's really important to win, it doesn't matter what the game is, because it brings confidence to everything you're trying to achieve as a group, attack or defence. Winning shows it's working.
"We've had three different sort of defeats and if we'd been beaten in the same way every time we'd be more worried.
"I think we're still in a good place in terms of confidence so we're hoping for a good game and a win at Harlequins on Friday.
"Then it's back into the league, two big games to try to get ourselves back into the top four."
Saints came back from 26-7 down at half-time to draw level with London Irish last weekend.
But the concession of a fifth try late on ensured the black, green and gold would be beaten in the Premiership Rugby Cup clash.
"In that first half we gave away too many opportunities in our 22 with our discipline," Vass said.
"As soon as you're in your 22 it means it's only a missed tackle or a system error and it's a try - there's no real out.
"There were similar opportunities at each end of the field and they took theirs but we didn't in that first half.
"Our discipline let us down.
"There were a lot of people who had never played together and it showed in that first half.
"We were better in the second half and we were better organised.
"We won the half but we didn't win the game in the end."
At Monday night's season ticket holders' forum, Saints boss Chris Boyd tipped Vass to become a 'world class defence coach'.
But although he enjoyed the praise, Vass wasn't getting too carried away.
"It's nice that he thinks highly of me," he said.
"Still, you have to be able to prove it by getting hold of a team and delivering the best defence you can.
"You have to maintain that level over a period of time and I think we are getting somewhere with our defence.
""We've reached a certain level, a plateau and we need to be at that next level if we want to be a consistent top-four team.
"The challenge is to get there but we're definitely not there yet."
Saints will now look to get back on track against Quins at the Twickenham Stoop on Friday evening.
"They're probably the best from turnover ball, they move the ball really well from any sort of errors," Vass said.
"It's going to be about how we react to any errors and how we transition from attack to defence.
"They can be a very quick team and they finish really well from any sort of linebreak because their support play is really good. They've always got three or four people around any break.
"Our ability to chase back, cover any errors and our scramble defence is probably as important as our frontline because they create a lot of opportunities for themselves."