I think the Support jobs can work, if they share Slot in the duty finder with DPS. I repeat only in the "Duty finder", in the FC/Party finders, this jobs will cause more sorrows than joys.

Support jobs will do 1/2 damage of a real DPS class, limitating the damage their weapons and buffs.

The negative aspect of this.

1.- The support jobs will cause longer waiting timers in all the content.

2.- The support jos will STEAL spots to the DPS in party finder and end game Free companies.

3.- How many times a terrible pug bard or corsair, joined to your End game group in FFXI, auto earning one spot in the main ally?. People were there years working hard, was removed in order of get the new "Support job guy". So please avoid real support jobs in this game =/.

Red mage = Healer & small Debuff capabilities = Healer Role
Dancer = DPS with a Small Healing capabilities = DPS Role
Blue mage = DPS 100% or Tank 100%
Corsair = DPS with small buff capabilities = DPS role
Geo = DPS with Small debuff capabilities = DPS role