A suggestion that may help is to determine either a primary leader of each group or a random rotation of people in the group. For the primary leader, have the rest of the people in that group following his orders, such as "Attack that ogre" or "Launch a fireball at player x" where that entire group sort of adds to what the leader does somehow, whether it be running interference, forming barriers, gathering assessments to be tagged, etc. For the random rotation of people in the group, just focus on what the current person would do and the rest are helping somehow or milling about, then next round it is the next person in the rotation's turn to do something. This gives the background some variety while not being overwhelming. Assuming the random group idea, if they work together, maybe add +2 to the current person's roll to signify that the rest of the group is somehow helping that person.