Far Shot

Far Shot is a keyword found on several item modifiers, on monster as well as Ascendancy passive skill of the same name.

Mechanics

As the projectile begins to move from its point of origin, the attack gains more damage, capped at 60% more damage. It is important to note that damage scaling is done with respect to the total distance the projectile has travelled, not its current distance from the point of origin. If the projectile changes direction—as is the case with Spectral Throw—distance travelled continues to increase as the projectile returns to its point of origin.

According to 3.13 patch note:

Interactions

Point Blank

Point Blank and Far Shot are multiplicative together (since they are more/less multipliers), and thus helps counteract the damage falloff at distance.

Longshot

Longshot functions similar to Far Shot, but instead offers increased Damage instead of more Damage.

Due to the additive Nature of "increased" modifiers, making a general Statement on it's overall benefits is impossible, as every Build has different Amounts of "increased" Modifiers.

If you take Far Shot due to wanting to deal better with Enemies at Range, then Longshot certainly is a good choice as well.