Opener Liam Rukuwai took 2-21.
"For me, Leopard was outstanding because he's come into the team mainly as a batsman," Diack said.
In reply, NTOB stuttered before eclipsing the target with 73-6 in 19.5 overs.
No 3 Greg Hay stopped the rot with 35 runs while CHB bowler George MacPherson took 3-14.
At Anderson Park, hosts Bayleys Havelock North CC were "more than rapt" to secure third place despite a gallant effort from The Station Napier Old Boys' Marist to cling to a losing draw.
"They had extra seven overs to go for a win but they didn't," Havelock North captain Jared Priest said, after his NOBM counterpart, Bevin Pollock, opted to play it safe.
"I thought they had just as much chance to score the winning runs as we had of taking the last wicket," he said, after NOBM were 133-9 chasing the villagers' 159 all out in 46.1 overs and veteran batsman Daniel Drepaul looking solid.
Havelock No6 William Hilton, an Englishman, scored 72 from 111 balls and No5 Rokon Al Sahariar added 35.
The loudest cheers were saved for No11 Jeremy Ketel, unbeaten on 11, after he hit a six.
"It was Jeremy's first six ever and he got it against CD spinner Marty Kain so that's even better," Priest said of Ketel who built a 54-run partnership with Hilton for the last wicket.
NOBM seamer Anoop Renuka-Prajad took four scalps for 31 runs while medium pacer Sam Prescott took four for Havelock North.
"Sam's taken 18 wickets in the 55-over format to become the leading wicket-taker by a distance in the premier competition so far," Priest said.
It was the first game at the villagers' ground this summer, marked with a club day and new prem team sponsors after the Hastings District Council's sterling effort to upgrade the wicket and outfield.
In the battle for the wooden spoon, Sharpies Golf Range Taradale CC beat Heretaunga Building Society outright by 123 runs at Nelson Park, Napier.
It was a case of deja vu for the visitors as they succumbed to defeat with three balls remaining to clinch a losing draw.
However, Dale captain Luke Kenworthy wasn't sure if their 12 points from the win was enough to leapfrog Cornwall for the wood spoon.
"I think they never looked like chasing it down right from the beginning," Kenworthy said as Cornwall were 100 all out in 54.3 overs with Nathan Worlsey scoring 28 runs.
The Maroons amassed 223-5 in 55 overs with No 4 Kenworthy laying the foundation with an unbeaten 132 from 144 balls, including seven fours and eight sixes.
No5 Callum Hewetson added 56 to the cause.
It was Kenworthy's maiden premier club ton. He scored 99 against NTOB two summers ago in an NZ club championship game which Taradale lost.
Pay Excellence Hawke's Bay senior men's representative Kenworthy is showing form after he was 80 not out against Havelock North the previous Saturday.
Cornwall's Jayden Wiggins maintained his fine form with 4-34 from 11 overs but the kudos for the weekend belonged to Dale's Ben Stoyanoff who claimed 7-36 from 16 overs, including four maidens. "Ben spearheaded our attack and he bowled a great line," Kenworthy said.
