This is true to some extent even in other mmos, theres a reason for this.

Any damage action is taken to the battle log, so lets use this example, 24 players, all aoe at the same time on a pack of 30 mobs, do you know how aggravated the battle log will be, the info will need to be processed locally on the memory and cpu (ps3 limitation).

Other mmos employ a damage reduction but you can get a truck ton of adds but the damage evenly spreads after a point in order to clam down this process. Any one thats done the Onyxia many welps handle it achievement will understand XD.