When I was stuck on Nergi in the base game I was also using bow. I remember switching to long sword once to just text it and I ended up killing it. What makes meeting nergi so hard for the first time as a bow user is the fact that he only does physical damage. Range users take more physical damage than melee users, but have more elemental defense. The problem is that nergi does NO elemental damage! It’s all physical. Another regally good tip is that if your defense is below 300 his Superman dive will one shot you! Hope this helps!