Mitch Nichols' brace and a James Troisi goal sealed the result for Victory before a Nicholas Kalmar header softened the scoreline.
But it was Kisnorbo's 20th minute red card that transformed a potentially tight contest into a Victory walkover.
Despite starting best in a scrappy opening - Michael Mifsud twice missed chances while through on goal - Heart were reduced to ten men when Kisnorbo's studs-up lunge at Connor Pain missed the ball and found his shin.
The tackle was as reckless as it was unnecessary - while Pain had passed three Victory players Kisnorbo had good position on the Victory striker, and a standing tackle would have sufficed.
Victory had barely threatened to this point and could have been behind when Harry Kewell picked out an unmarked David Williams.
The resistance coming to an end, Heart keeper Andrew Redmayne could have claimed an assist on Nichols' opener.
A thoughtless clearance landed straight at Mark Milligan's feet, whose first-time ball played in Nichols for an easy put-away.
With Heart's shape lost in the transition to ten men, Victory piled forward, with Pain - a late inclusion for Archie Thompson - forcing Redmayne into a sharp near-post save.
After the break Kewell had his best moments of the match including a neat turn and shot forcing Nathan Coe into a low dive.
Their efforts repelled, Victory stopped playing with their catch and instead put Heart to the sword.
On the hour-mark, Troisi finished sharply from a Nichols' cut-back, beating Redmayne at the near post.
Three minutes later Nichols had his second, driving forward and playing the ball to substitute Gui Finkler, who dinked the ball back to Nichols to finish past the stranded keeper.
The contest killed, Kalmar had a goal he knew nothing about when Coe's missed clearance bounced from his head into the empty net.
Heart boss John Aloisi was scathing of referee Ben Williams' performance.
"In my opinion the referee had a terrible night," he said.
"He didn't control the game at all ... it doesn't make sense but he's the referee, he knows what he's doing," he added tongue in cheek.
"Debatable whether (Kisnorbo's tackle was) a red or yellow, I just think there needs to be consistency."
Muscat credited his players for remaining patient until they broke through.
"In the second half we moved the ball along their back four with a lot of speed, and scored some very good goals in my opinion," he said.
"Having played in some derbies myself I know they are very difficult games to win so I'm immensely proud of the boys."