Jadon Sancho appeared to have sealed the three points for the visitors until a Thomas Delaney own goal levelled the score for Eintracht Frankfurt with just two minutes left.
And while Reus admitted his side lost their focus towards the end of the game, he hit back at claims they are lacking in mental strength.
"It's getting on my nerves," he said to Sky. "The own goal was a mentality problem? We defended stupidly in that situation, of course, but don't come around with your mentality s**t now.
"Every week the same s**t. This is about good defending and knowing that Frankfurt always can come back even if we are 2-1 up.
"We just have to stand against it better in the last five minutes. I don't know how the equaliser came about. I think by a throw-in, where we put ourselves in danger. That just can't happen.
"But do not come with mentality stuff, please!"
Dortmund coach Lucien Favre reiterated Reus' message when he was asked about the team's mentality.
"It has nothing to do with it," he replied. "We had more opportunities to score goals.
"You can't completely dominate a game for 90 minutes, it's currently not possible. It's the same everywhere, I watch other games."
Centre-back Mats Hummels was taken off shortly after the hour mark, and Favre confirmed the Germany international was experiencing some discomfort.
"He could not move properly and could not sprint anymore," Favre said. "I can't say more than that yet."