We didn't see a big rotation from Leverkusen in their DFB Pokal game against Paderborn yesterday. The strongest rotation was in the defense line as the goalkeeper and defenders were all different than their previous league game. The rest of the lineup was pretty much the same. They got a decent win and moved on there.
Stuttgart played a much more difficult game against Dortmund on paper. However I was still expecting them to eliminate Dortmund and they really did it.

Stuttgart are in a better condition than Dortmund now and I expect them to be very ambitious in the DFB Pokal cup as well.
I think even if Leverkusen uses second tier players they will still win and this is proven by winning by a 2 goal difference in the DFB Pokal match and this also continues Leverkusen's unbeaten trend in all competitions.
Stuttgart is still the strongest even though their opponent is Dortmund and perhaps no one would have expected if they beat Dortmund with a score of 2-0 without reply. Actually I expected Dortmund to be a little more serious in the DFB Pokal competition but it seems they also had difficulties against Stuttgart who are currently in their best form. This was Stuttgart's second win when they met Dortmund after previously they also managed to beat Dortmund in the Bundesliga three weeks ago.