The traps need focused retraction and depression work to prevent imbalances. For this exercise, start in the regular seated row position while making sure the back is arched and the chest pushed up.
From here, squeeze the shoulder blades together and hold for several seconds. By focusing on pushing the chest up and out, the shoulder blades are more easily depressed.
Sure all the pros are roided out to their mutant gills. That doesn't mean we can't still learn some incredibly valuable back-training tips by observing how the big bastards train.