Coming back to the OP's original question, imho, "It depends". In the case of Sagani, since she has a talent pre-spent, it's better to either focus on the hunting bow, or abandon bows altogether. If you're going to "eat" the talent and move her to a new weapon group, you may as well move to arbalest or arquebus, since you get added bonuses(inherent DR bypass, knockdown on crit), as opposed to just being a slightly harder hitting hunting bow. Regardless of choice of weapon, I think Penetrating shot is a bit of a waste for a Ranger, since they get two superior modal abilities for ranged dps in Swift Aim and Vicious Aim. Swift Aim is great if you set your ranger up with per-hit bonuses like elemental damage or Marked Target, and Vicious Aim gives you roughly the same damage boost as Penetrating Shot(+20%), with the added bonus of +10 Accuracy and no diminishing returns against low DR enemies. Let's be real though, Eder and Itumaak dialogue makes Sagani worth keeping in the party, even if she was spec'd to be as sub-optimal as possible. Eskimo-Dwarves ftw.