You see the logic for the BLM nerf fails in mainly one respect, and most Melee are way too blind to see this.
Shortened list, just for arguement's sake:
Paladin:
Defense: A+
Melee Damage: F
Magic Damage: F
Party Support: D (The ocasional Cure)
Survivability: B
Purpose: Single point of failure in Party/Defender.
Dark Knight:
Defense: C
Melee Damage: A
Magic Damage: D
Party Support: F
Surviveability: C
Purpose: Melee Damage, Skillchain.
Bard:
Defense: C
Melee Damage: F
Magic Damage: D
Party Support: A+
Survivability: C
Purpose: Enhance Party's abilities.
Thief
Defense: B (Evasion)
Melee Damage: C
Magic Damage: F
Party Support: F
Survivability: A+
Purpose: Hate control, Skillchain.
Black Mage
Defence: F
Melee Damage: F
Magic Damage: A+
Party Support: D- to C-
Survivability: F
Purpose: Damage.
Basically, Black mages don't do anything except for damage. they are not built for anythign else. Having a BLM nerf would be the same as having a PLD Defense nerf; it just doesn't make sense.
Why then did they nerf Ranger? Well I would assume it was for the reasons they gave the public, Paraphrased: the job was considered Melee, and it had an inhearant disproportionate advantage over other melee in it's Class. (WAR, DRK, SAM, DRG I.E. The Melee portion of the Damage Equation). So in order to bring balance to that Segment, it needed to be nerfed. Personally, I think they went too far.
What you tend to see later when you do things like fight HNM and what not, is the roles of the jobs. Melee is there to pretty much Set up the Skillchain almost Exclusively. As exclusively as it is the WHM's job to heal, and the BLM's job to do the Dmg...
After giving it more thought. I was trying to figure out why Thief wasn't 'enhanced more'. And I came to the conclusion that if Thief were enabled to do more damage that they would offset the party capabilities way too much. Remember, every point of damage a thief does is a point of damage every single DD can do in the Party. Thief TA's a Shark Bite for 300 damage in an Alliance with 8 Black Mages, that thief basically created a damage potential of 2,400 Damage. If thieves did TA 1,000 Damage, that's 8,000 Damage the rest of the party can do. And Since TA is a Subbable ability, that problem carrys over to all other melee, making Enhancing Melee with TA more of a problem than one would initially think.
When you think about things more, you start to see BLM is one of the Few jobs that is working 100% according to spec.
Ranger Nerfing on the other hand was only needed in the vane that they were delivering a paced 200+ damage a shot (Every ~4 seconds) Have Barrage, An insane TP gain, the ability to SC on moving targets. This was a severe imbalance. HOWEVER... Again... they went too far. Way too far.
There are other aspects to the Melee Field that people in general over look, they require a lot more skill and timing, but nothing like learnig how to lay out your first Skillchains in the dunes when you started the game. Melee can be severely Overpowered... If you know how...