Teenage winger Ash Handley scored a hat-trick of tries as the Rhinos capitalised on a flying start to make it six wins in a row.
“We’d like to be eight clear, we’d like to be 10 clear, we’re not looking behind us, we’re looking forward and trying to get as many points as we can,” McDermott said.
“I think everyone would say there’s a bit more improvement in us.”
Leeds never looked back after establishing a 28-6 half-time lead but the introduction of Australian scrum-half Luke Walsh helped galvanise Saints, who cut the gap to 12 points at one stage thanks to two tries from centre Jordan Turner.
“Collectively we were very good,” McDermott said. “It was a great team performance.
“I didn’t think we were in as much control of the game as the scoreline indicated at half-time.
“We still had some work to do in the second half. Saints pretty much threw everything at us. We found that second half unbelievably tough.”
McDermott opted to start with skipper Kevin Sinfield on the bench - for the first time since 2003 - with Liam Sutcliffe continuing his impressive bid to become the club’s long-term successor to the former England captain with another polished, creative performance.
“He came up with one or two things that broke the first game, especially in the first half,” McDermott said. “Add to that, he showed a fair bit of control.
“Kevin was very professional. He’s 100 per cent behind us and he wants this team to do as good as it can do.”
Saints’ fightback was snuffed out by late tries from Sutcliffe and Joel Moon as they crashed to a fourth defeat in five games.
Coach Keiron Cunningham admitted his side paid a heavy price for their first-half defensive errors.
“Our marker play was extremely poor, we became victims of our own errors in defence,” he said. “You can’t give as good a side as Leeds so many chances around the ruck. They’ve got a great nine and a lot of good support players.
“Resilience and scramble is always very good from Saints but our ruck defence let us down massively.
“The frustrating thing is that when we came out in the second half after speaking about it at half-time we turn into a different side. If we had done that in the first half, I am sure it would have been a completely different game.”
Cunningham defended his decision to reintroduce Walsh gradually following his eight-month injury absence, revealing that he will start next week’s game against Widnes.
“There was always a plan to introduce Luke Walsh back into the game,” Cunningham said. “He’s come from a very severe long-term injury and I had to hold my nerve.
“We’ll start him next week. I knew he’d make a difference in the game because he’s a great seven.”