Balthier has low magic and mp growth with I think Basch (the game's obvious melee character) having slightly lower. Balthier has the third highest strength and HP growth behind Vaan and Basch but scores the highest speed stat, making weapons like daggers and Ninja blades better for him. In Revenant Wings, he has decent attack power and high defense from his armor types. His range is really good but frankly Kytes, the game's actual blackmage is a better Range Unit due to exploiting elemental properties and having AoE abilities whereas Balthier is basically comparable to Vaan or Basch just a ranged fighter. In Tactics: WotL. Balthier's stats are similar to his XII incarnation when using his default Sky Pirate job. The job is an odd mix of Thief, Machinist, and Knight giving it high speed and good strength and HP growth.
Guns, in all of the Ivalice titles, work the same with sporting low attack power but ignoring defense making them pretty comparable to most melee weapons beyong high level mystical weapons like Excalibur and the Zodiac Spear. There are magic guns that fire spells but their power is in proportion to the wielders MAG stat making them a bit underpowered in the hands of say... Balthier and they also suffer from some of the short comings of the gun weapons themselves like needing a direct line of sight in order to hit. The magic guns also had an odd critical hit elements where the spell would do critical damage by summoning tier 3 versions of the spells they cast.
Whoops, my bad. I knew guns existed in XI, I just forgot there wasn't an actual job that specializes in them.
**************************************************************************************************** ***
If you're looking for an RPG series that really justifies guns as a weapon to be reckoned with, I would play Wild ARMS. The first game treats guns as dangerous mythical weapons, the second game involves the main character using a rifle/bayonetta as his default weapon which works as a both a sword for regualr combat and as a gun for special skills.