A hat-trick from Aubameyang saw Dortmund to a 4-0 win at home on Wednesday, completing a 4-1 success on aggregate in the Champions League last 16.
Aubameyang was criticised after the opening leg, during which he missed a penalty, and Tuchel was thrilled to see improvement.
"If I say that I expected this result it would mean that we have a lack of respect for Benfica. You cannot expect that you will score four goals against a team like them," he said, via UEFA.
"We had the self-confidence to turn the tie around and the team demonstrated that, especially in the second half.
"We saw the real Aubameyang [as opposed to the first leg].
"Benfica are a great, proud club and we have huge respect for them but we played two great games and I think we deserved to go through. If you are into the last eight you want to go to the last four and that's what we will try hard to do."
Aubameyang struck in the fourth minute before Dortmund took control in the second half, the impressive Christian Pulisic doubling the lead before the Gabon international completed his hat-trick.
Benfica coach Rui Vitoria rued going behind early and felt his team had enough chances to reach the quarter-finals.
"We did not start well into the game, conceding so early," he said.
"But we did well after that and played nicely, until we allowed them to score two within a few minutes.
"Everyone could see that the game went well for us and that we could have gone through, we did have our chances after the break and didn't use them. Then we were hardly able to react."