The balance wasn't really the reason.
But there are multiple other reasons:
1.) We don't like it when a hero looses parts of his set by normally leveling up.
When it's just a small ability which is replaced by a stronger one, even though it's different, it's okay. But when your hero looses his ability for something important like ranged attack, it feels kinda weird. He levels up and therefore gets weaker? After leveling up he has forgot how to use a bow?
Seems a bit weird.
2.) Aragorn doesn't have animations for a ranged attack.
We like his current animations as it's iconic and unique in Gondor. We would have ro replace all of his animations (even in melee fighting) with Faramir's animations. That's also something we don't want, because we think that those animations wouldn't fit to Aragorn.
3.) We want to focus heroes around their core identity.
Of course you can argue what is important for the core identity, but we don't really like to add abilities because they were shown one time in a movie without having any big impact.
If we gave Aragorn a ranged attack, we should also give nearly every hero in Gondor, Lorien, Imladris and the Dwarven faction a mount. Every hero was shown at least once riding. Additionally at least Thorin should also get a ranged attack.
And so on... you see where this is leading? Dozens of abilities without fitting animations and without really helping you much in the game. And we would have to delete abilities for nearly every unit, as we need the slots for those abilities.
Therefore:
No, we won't add a ranged attack for Gondor.^^