It comes doesn't to jobs people want in raids and speed kills which is where you see the actual balancing issues...

Top tier - DRG/BRD/MCH/NIN

MCH may pose an issue with ping but if ping isn't an issue is a great dps. This group is your buffing team they provide alot of rdps which isn't negligible..

Mid tier - SMN/MNK/RDM

These classes have a decent amount of dmg, small raid buffs that can be negligible, RDM dmg is really low for the utility it offers and sometimes is only a great class for progression purposes.

Low tier - SAM/BLM

Your highest personal dmg classes but provide the least amount of buffs if any at at all, usually labaled persona non grata as they take up spots for classes who offered more which currently is at a higher value than classes who offered nothing...