Sunny did not shy away from using the power of his subordinate Saints, but there was a limit to how effectively he could handle them. After all, they were spread across the long frontline — even though he could move with startling speed, he still had to reach a Saint and explain what he wanted them to do, which took time.
His Shadows, however, answered his mental command and knew exactly what he wanted from them without the need to use words. In addition to that, each of them was also more fearsome than any of the Saints under Sunny's command.
Therefore, they acted as the three pillars of the entire offensive, moving ahead of the soldiers to defend them from the more powerful foes.
Unlike Sunny, who moved constantly from one threat to another, his Shadows mostly remained in rigid positions relative to the battle formation of the war party, and drew the threats to themselves instead.