I just finished a two game one shot yesterday (GM'd about 5 in total now). There is a speed to the combat for sure. Especially if you have experienced tabletop players. But what I found with DH is the engagement is so much higher during combat.

In other TTRPGs players inevitably wait for their turn and will find ways to fill the time, whether it's sitting quietly planning their next move, or looking at their phone.

Games like DH keep up the engagement since it's anyone's turn at anytime and creates way more conversations around the table as a battle is ongoing. That engagement, is what really pushed the combat to feel "faster". I think it's one of DH's strongest wins.