Lions and Ireland No8 Heaslip was hugely influential throughout, with his power, pace and sheer commitment in both defence and attack setting the platform for a hard-fought 32-23 triumph over the four-times continental kings.
And Heaslip, who tasted defeat against Toulouse at the same stage of last season's competition, insisted he and his team-mates are now determined to push on and establish Leinster as one of the great Heineken Cup sides.
"Winning things builds the legacy of a squad," said Heaslip who joined skipper Brian O'Driscoll and 19-point hero Jonathan Sexton on the scoresheet.
"We're trying to build an organisation that is successful and we're constantly producing really good players.
"I don't think we played our best rugby, but it's no guts, no glory."
That glory was sealed despite the worst possible start to proceedings when Florian Fritz crossed for a fifth-minute try.
Leinster hit back via Heaslip's close-range score on the half hour and, although Toulouse re-established their advantage through Louis Picamole just after the break, the hosts kept their composure to reach this month's Cardiff showdown.
The defensive effort throughout the entire encounter was monumental and nothing summed that up more than when Heaslip somehow stole possession from Gregory Lamboley to bring an end to wave after wave of Toulouse attacks with less than 10 minutes remaining.
"Isa (Nacewa) made a great tackle and that presented an opportunity to get on the ball," was Heaslip's modest assessment of that critical moment.
"We've been working hard on getting the second guy in and trying to get turnovers. I think we've been pretty successful at that.
"It was a tiring affair. We had a lot of tired bodies out there at the end but we were just focusing on the next job, not on the next five minutes but just on what we had to do in that moment.
"Toulouse played some amazing rugby. They showed us last year when we played them in the semis what they can do, and they had glimpses out there again this time. They moved us round the pitch and made us work hard.
"Both teams had their purple matches. I don't think there was much between the two teams but we're just happy we've made it through.
"Going forward, we'll have to take a look at the video because I don't think we played our best rugby. And to win this tournament, we'll have to be at the top of our game."