Like almost Def unit, Bennet possess a good endurance. Her Skill are:
Wild shot (weak single target attack that reduce target atk).
Counter bomb (counter enemy attack by attacking both right and left of unit target)
Iron will (increasing both atk and def at 50% or less HP)
Rampage rush (Special that attack row of enemy unit with 100% chance of stun for 1 turn)
Bennet is meant to take as much punishment as possible while countering enemy with her counter bomb then stunning them. Even though her damage output is somewhat small, her special gauge will be filled very fast. thus she could spam her rampage rush quite often. A very good choice to counter healer or backline heavy hitter by stunning them. pairing her with healer is very beneficial for her as she can be more sturdy and hit harder after iron will activated while recovering back her lost HP.
Her preferred placement is off course the slot that will be attacked most. place her in front of enemy formation that form a row.
As mentioned above Bennet damage output is somewhat small before iron will activated. Reilly on wild shot alone wont be doing much.Thus the best counter is to slow her special gauge fill by placing only single unit in front of her. Due to the range of her rampage rush, at best only 1 unit will be stunned. This problem can be solved by placing dps behind her to kill her opponent fast enough so she can lock on other target that most likely forming a row.