If have to split one buff for mages, and one for melee, why take a GEO over a bard? And for the nuking side, why take a GEO over a BLM or SCH?

As it is, party composition would determine where a GEO should be currently. Unless in a mage heavy group, GEO looks to be most effective close to the mob as that is where most members of the group would be so buffs are on most of the group.