Two goals from Pierre-Emerick Aubameyang as well as goals from Lukasz Piszczek and Dembele helped Dortmund to a comfortable win at Signal Iduna Park.
And Tuchel was elated with the all-round contribution of his team, with Reus - who set up three of the goals - and Dembele especially impressing their head coach.
"I think we put in a very complete performance against a team that is very difficult to play against," the trainer told reporters.
"We can withstand criticism. Internally, there was much less pressure on the side than there was in the public.
"We have, over 90 minutes, played with aggression and we were compact. I think that was the key.
"It's amazing how Reus has returned, and Ousmane Dembele, in my opinion, had one of his best games for Dortmund."
Aubameyang's double takes the Gabon striker to 15 Bundesliga goals for the season.
And the 27-year-old acknowledged that, while he is determined to help the team achieve their collective goals, he is also focused on finishing the campaign as the league's leading scorer.
"We won the game and that is all that matters," Aubameyang said.
"I'm in a good way at the moment. I have to keep going and keep fighting - for the team but also for the race to be top scorer.
"I'm a striker. I want to help the team, yes, but I want to win that race as well."