I really don't see what's wrong with this item.
Many jobs have nothing, or next-to-nothing to wear in the Ammo slot until way later in levels, when you get things like Bomb Cores, and such. DEX+1 and AGI+1, while very small bonuses, are better than nothing at all. Many jobs have nothing to wear in the Ranged slots, such as Dragoons, Monks, and other jobs.
DEX, while a small bonus, does help accuracy. .5 ACC for a One-Handed weapon, or .8 ACC for a Two-handed weapon.
AGI, while a small bonus, does help evasion.
I can assure you that -anyone- could benefit from this item, regardless of job, unless there is a better item instead.
For MNK and DRG, there is next to nothing else to wear in this slot, except what, Pebbles? How often does a MNK or a DRG actually get asked to pull?
For Mages, the only other thing is a Morion Tathlum, but not everyone has one of those. If you don't have a Morion Tathlum, this isn't bad either. AGI+1 is better than absolutely nothing.
For WARs, SAMs, NINs, DRKs, etc who *can* equip a Ranged Weapon, if you are not the puller, then there is little other reason to not equip this, unless you intend to use Acid Bolts (which NIN cannot do). I don't know too many NINs who tank and pull (pulling always brings with it, the danger of losing shadows on the pull), so it is likely you will be pulling as NIN. Other than trying for a few extra TP while throwing a chakram, I see nothing else a NIN would want from her ranged slot at Lv30. AGI+1 would help her EVA, and DEX+1 would give .5 ACC. Both of which a NIN needs. For SAMs, unless you are the puller, or seriously trying to squeeze out extra TP from ranged attacks, there is absolutely no reason to not wear this. .8 ACC helps.
So, in the end, the only jobs I can see who DON'T want to wear this:
RNG: They are constantly using ranged attacks and cannot afford to give up their ranged slot for this. Attempting to macro this in is still useless, as it wipes their TP.
PUP: The Animator goes in the same slot.
Puller: Obviously, if you are pulling, you are using a Ranged Weapon.
WAR/THF/DRK: If you have Acid Bolts, you are probably using those instead of this. If you do not have Acid Bolts, and are not the puller, use this instead. DRKs could even pull with Poison if they wanted to, again, the .8 ACC thing.
Mages: If you don't have a Morion Tathlum, use it. If you have a Morion Tathlum, use that instead.
Otherwise, if you have this, use it! I mean, what Else are you gonna put in that slot? Pebbles?