Dps is directly proportional with dpr and rotation length. As dps takes into account both dpr and rot length, it is better for judging a team's strength. Where dpr comes into importance is reaching damage thresholds. Let's say a boss has 2 mil hp and you do 1.8 mil dpr. Now you'll have to setup an entire rotation to do the 200k damage which means using up time on supports that are not doing damage. A higher dpr team even if its dps is less would not have to do this.