Dortmund have finished in the top-two in the past four seasons in Germany's top flight, including back-to-back titles in 2010-11 and 2011-12, however have opened the domestic season poorly.
Jurgen Klopp's side climbed off the foot of the Bundesliga table with a 1-0 win over Borussia Monchengladbach on Sunday, but are 13 points off a top-two spot - and 17 shy of leaders Bayern through 11 matches.
Wolfsburg sit just four points behind Bayern in second spot.
Heynckes, who in his most recent of three stints in charge of Bayern took them to UEFA Champions League and Bundesliga success, said Dortmund's struggles meant there was a lack of "tension" in the title race.
"Of course, the tension has reduced a bit," Heynckes told Perform.
"When the championship is already decided in advance and you can tell that Bayern is going to win the championship easily, an objective spectator might be disappointed.
"Talking about the title race, there's certainly a lack of tension. But that's not Bayern's fault. They did their homework and got a great squad. They're dominating the league.
"Dortmund's bad start has led to a situation in which Bayern has no competition. I wouldn't have expected that.
"It was obvious that Dortmund's players would come back exhausted from the World Cup, considering their style of play.
"For me, it was possible that some of their players would perform a bit worse than usual, but in this case you have to make the right adjustments.
"You need to have a squad which can compensate for this. But no one expected this performance from Dortmund."
Heynckes claimed the squad he took to European success in 2013 was the best to have represented the Allianz Arena outfit, and said they have only built on that under Pep Guardiola.
"After the defeat in the Champions League final in 2012 against Chelsea we set up the squad, got more quality in the team," Heynckes said.
"Then we had 2013 - the best squad in the history of FC Bayern Munich.
"And the organisation continues in that way. They added Mario Gotze and Robert Lewandowski who certainly are two of the most wanted players of the Bundesliga.
"Xabi Alonso came to Bayern as well. When he played in Liverpool and in Madrid, he always performed at a world-class level.
"So, you can see, the quality of Bayern's squad is better than anyone else's in Germany and that's the reason why they're dominating the Bundesliga and why they won the title last season.
"They also haven't had to worry so far in the Champions League. They are already qualified [for the knockout stages] and have a huge chance of winning the tournament this year."
Bayern have won all four of their Group E games so far despite being drawn in the toughest group in Europe, and cannot be caught in first place.
