Either SMN and RDM should lose their Raise or BLM should get a Raise.

[TelosNox]

So, on progression, where deaths are a real threat, if BLM's personal DPS doesn't compensate the longer downtime on dead people, it's understandable to take a RDM that can raise 3 people in 6 GCDs.

RDM with 340 gear has about 14500 Mana. From my latest parse in fflogs I see that RDM consumes about 4k Mana per minute (just his own skill, no mana shift, no raise - and yes I play efficient, I am at 96% in that parse).
Lucid Dreaming restores 6720MP every 2 minutes. So without any external Mana a Redmage consumes about 1300MP in 2 minutes that he can not restore.
Raid Boss fights are about 10 Minutes. So RDM will effectively consume 5 x 1300 = 6500MP until end of fight if he uses Lucid Dreaming on CD. So he has about 8k Mana left over.

Raise is 3,6k Mana. So 3 Raise in a Row will be 10,8k Mana. If you do 3 Raise as RDM (not necessarily in a row), you will end up doing no dps for the last 2-3 minutes if there is no other who provides Mana for you.