"These commandos excel at infiltration, rushing past fortifications to attack vulnerable resource buildings. While fast, Pathfinders are lightly armored, and vulnerable to turrets and starship strikes."
~In-game description of Rebel Pathfinder
Rebel Pathfinders destroy Resource buildings faster than normal Soldiers. Combine that with their speed and you have a very useful unit for spread out resources. Light units also need screening, so make sure you distract turrets with bruisers or other turret killers, otherwise these troops are wiped out in seconds.
Pathfinders don't belong in defense, as they are killed easily and don't do as much damage as Strikers like the Speeder Bike