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Pioneer's vision bonus impact is simply exaggerated. The unit is overburden with number of tasks so it not very practical to be used as scouting while the number produced in early game is simply very limited due to their limited combat capabilities.
IS vet 1 ability has more impact then pioneer vision.
As for pathfinders/I&R pathfinder the units should remain at CP 0 so it easier to fit on USF build but their initial power and cost should imo go down.
Imo they should start with 4 long range rifles and have to upgrade to scoped rifles, while becoming cheaper. They should also have their XP value increased. Finally the off map could become cheaper/less powerful while locked behind tech or vet.
Imo these types of units should be support units instead of core units.