With all eyes on Tuesday's Champions League clash with Real Madrid, Bayern rested several key players, giving first-team debuts to the 20-year-old Dorsch, as well as teenagers Meritan Shabani and Franck Evina.
Dorsch gave Bayern the lead from close range just before half-time, and Sandro Wagner doubled the lead in the second half. Sebastien Haller grabbed a goal back for Frankfurt, before Rafinha and Niklas Suele wrapped up victory for the hosts.
Bayern will face Frankfurt and Kovac again in next month's German Cup final in Berlin.
Nils Petersen scored a goal in each half to give Freiburg a comfortable lead, before a dramatic late comeback from Cologne.
Leonardo Bittencourt netted two goals in five minutes to give the visitors hope, but a late strike from Lucas Hoeler sealed Cologne's fate.
Fellow strugglers Hamburg, meanwhile, fuelled hopes of a miraculous escape with a 3-1 win in Wolfsburg.
Bobby Wood fired Hamburg ahead from the penalty spot on 43 minutes, ending his 247-day goal drought.
Lewis Holtby doubled the lead moments later, nodding Tatsuya Ito's cross into the far corner. Josip Brekalo pulled a goal back for Wolfsburg 12 minutes from time, but Luca Waldschmidt secured victory in stoppage time for Hamburg.
Hamburg's third win in four games puts them just two points adrift of safety as they bid to avoid a first relegation in their history.
Elsewhere, Schalke drew 1-1 with Borussia Moenchengladbach, while Hertha Berlin rescued a point against Augsburg.
Schalke's Nabil Bentaleb was sent off early in the game, after appearing to slap Gladbach captain Lars Stindl.
Stindl then set up Raffael as Gladbach took the lead on 32 minutes but, in a cruel blow to his World Cup hopes, was carried off the field with an ankle injury before half-time.
Daniel Caligiuri levelled the scores with a penalty late in the first half.
In Berlin, Michael Gregoritsch's deflected shot looped into the top corner to put Augsburg ahead on 32 minutes, and Sergio Cordova doubled the lead with a well-placed shot on the hour mark.
A Vedad Ibisevic penalty and a late strike from Davie Selke, however, rescued a point for Hertha.