I agree with the way you're thinking about this, which is that FFTA and A2 have a ton of useless abilities that you would never use. I am a little sympathetic to abilities that you could at least use for part of the game before moving onto more advanced versions (e.g. fire->fira->firaga), but there's a ton of trash in there.
I think you only need to worry about certain jobs being overpowered if they're clearly always a better choice compared to another pick. You could solve that by either nerfing the OP job or making the underpowered ones more useful. If you can't come up with a worthwhile ability, cut it.
Reducing the number of abilities is not the only option you have available. Another option is to change the useless abilities to abilities that a player might have a use for. That's what I'm trying to do with the mod I'm working on anyhow (so long, Parley!).
I think you only need to worry about certain jobs being overpowered if they're clearly always a better choice compared to another pick. You could solve that by either nerfing the OP job or making the underpowered ones more useful. If you can't come up with a worthwhile ability, cut it.
Reducing the number of abilities is not the only option you have available. Another option is to change the useless abilities to abilities that a player might have a use for. That's what I'm trying to do with the mod I'm working on anyhow (so long, Parley!).