Dortmund chief executive Hans-Joachim Watzke hit out at Bayern Munich chairman Karl-Heinz Rummenigge earlier in the day for reportedly revealing that forward Reus - who is still recovering from an ankle ligament injury - has a buy-out clause of €25 million that comes into effect next year.
However, the controversy over Rummenigge's revelations do not appear to have affected Jurgen Klopp's men, who continued their unbeaten record in pre-season ahead of the new Bundesliga campaign.
Henrikh Mkhitaryan was the star of the show for Dortmund in Poland, scoring the opener and setting up striker Ciro Immobile for the second in a comfortable victory at the Stadion Miejski.
Substitute forward Adrian Ramos added the gloss to a fine performance late on with his first goal since joining from Hertha Berlin in June.
It took Dortmund just nine minutes to open the scoring, Mkhitaryan slotting into the bottom corner after surging towards the Slask box and playing an exquisite one-two with Pierre-Emerick Aubameyang.
Dortmund continued to press and their lead was doubled in the 20th minute, Mkhitaryan coming to the fore again by sliding a pass through for Immobile to coolly convert.
Aubameyang then drew a fine save from Slask goalkeeper in Wojciech Pawlowski at his left-hand post as the visitors sought to kill off an increasingly one-sided game with a third goal.
Both sides unsurprisingly made changes during the interval but Dortmund continued to dictate matters, Jonas Hofmann and Ji Dong-won both testing substitute home goalkeeper Jakub Wrabel in quick succession.
By contrast Ekstraklasa side Wroclaw never looked like threatening a comeback, and Dortmund's victory was sealed in the 82nd minute through a fine goal from Ramos.
The Colombia international cut in from the right before neatly combining with Hofmann, collecting the return pass and finding the net with a low finish.
