Each dps class has its own strength.
SMN able to dot multiple things
BLM king of AOE burst
MNK/DRG powerful single target
BRD very mobile and has a lot of utility

Melee dps are by far the highest dps on single target, ive been in parties with 2 MNK on Titan ex, and they could destroy heart phase before circle bombs! Never happens without 2 melee dps. (that is without LB)