Hussey especially had a strong game with some good carries, while Middleton twisted through tacklers near to the line to keep up his side's impetus.
With regular fullback Nick Harding on the bench due to a minor leg injury, Clare took on all the tactical and goal-kicking responsibilities, and by the third quarter had his side in full control of the territory, while a tired Marist were making errors on their carries among the furnace of the packs.
Losing reserve forward Dale Pene and prop Viki Tofa in close succession to the sin bin for rough play did not help their chances either.
Nonetheless, in their first semifinal in four years, Marist never gave up - keeping the scoreline under 40 points while having the last say with a well-worked try.
Looking to win their 15th straight home game and having expected rivals Byford's Readimix Taihape in the final, Border have improved their scrum, the pack delighted when they forced a handful of turnovers.
"Reasonably decent, I suppose, quite frustrating to watch – especially that first half an hour – probably a little bit of nerves as well, not quite trusting the system," said coach Cole Baldwin.
"But once we got that sorted, we were pretty good."
Baldwin agreed Hussey had stepped up.
"I thought all our loose forwards did well – him, Cody Wickham and Angus, as well as our whole forward pack.
"The scrum's getting stronger and stronger, we've been working on that for a team next week, but that doesn't seem to be the case."
While there was a palpable sense of pleasure around Dallison Park that Taihape had been upset by Wanganui Car Centre Kaierau, Baldwin has been to Cooks Gardens enough times as a player and coach to know that no game can be taken for granted.
"Kaierau are a good side, so it's going to be very interesting. They tend to hold on to the ball for long periods, so we've got to be disciplined around that breakdown area."
Marist coach Travers Hopkins was already looking to the future and what it meant for his side to finally be back in the Premier playoffs.
"I said earlier in the week we knew it was going to be a challenge coming up here, they've set the standard all season.
"At home, they had a lot of things going for them. But we didn't have anything to lose, and we showed a lot of fight, right to the end.
"A lot of teams probably would have shut up shop after being 20-odd points behind, but credit to our guys, they stuck at it."
If Marist have lacked for anything over these past few years it's continuity - constantly rebuilding under different coaches - but Hopkins is hoping everyone will be back in 2022.
"Some guys are obviously getting older. But for our young guys, first touch of semifinal rugby, I think it's good, it's encouraging, and I just hope we carry on building on that."
Border 39 (V Tikoisolomone 3, K Hussey, T Lennox, A Middleton tries; C Clare pen, 3 con) Marist 11 (C Botica-Teki try; R Kui 2 pen). HT: 20-6.
