The QTEs only occurred when you activated the execution mode which was done whenever a skull icon appeared over an injured opponent's head. The enemy would quickly have a blue (X) or yellow (Y) aurora about them, prompting a button press. For the purposes of the demo, pressing X or Y when the aurora was there would continue the combo, but the rep told me on normal or higher difficulties this wouldn't be the case. Other than that, I saw no QTEs.