Reus made a fine return from six weeks out with a thigh injury, registering the opening goal at Signal Iduna Park inside two minutes.
Although Marco Fabian equalised, a stunner from Sokratis Papastathopoulos was added to by Pierre-Emerick Aubameyang four minutes from time.
Reus was not on the pitch at that point, though, having been replaced by Ousmane Dembele at the interval, sparking concern he could be set for another spell on the sidelines.
"Marco Reus we changed just as a precaution, which was agreed beforehand," Tuchel said in a post-match news conference.
Sven Bender is a fitness concern, however, ahead of the midweek match having also made way at half-time for Matthias Ginter.
"Sven Bender had to come off. His thigh muscles were tight and the risk was too great," said Tuchel.
Victory saw Dortmund bounce back from successive defeats to Bundesliga leaders Bayern Munich and Monaco, the latter after an attack on their team bus prior to kick-off on Tuesday hospitalised Marc Bartra.
Tuchel feels the players are gradually coming to terms with the incidents that saw three explosions go off near the vehicle, and was proud of their show of support for Bartra, released from hospital on Saturday, following the final whistle.
"We played very courageously in every phase. We had good charisma on the field," Tuchel said.
"I had the impression today that we have all learned to deal with these feelings. I heard yesterday [Friday] from a professional that there is probably a threshold of two to three days to become emotionally stabilised.
"So I think for the players it is becoming easier to distract themselves if they can stand on the pitch and play.
"After the whistle and in front of the south stand, that was a great gesture from the team."