Because the ff14 developers are used to FF11 and other similar MMO theologies.
They could have easily done it like Ragnarok online, and have linear xp forumlas and have their true "many vs many" battles. There isn't a super-breed theory that you have to gang pile on an enemy.
Have to work within some built in confines of how FF14 formulas work or you'll have to completely redo it in the end.
