I fought Moder with a bow and iron mace. Didn't run out of arrows but my bow's durability dropped to zero just over halfway though Moder's health. I had to finish off the fight with the iron mace. It worked just fine. My mace wasn't fully upgraded, nor was the bow. With enough patience, and if you don't make too many mistakes, you can get through most boss fights with gear that's not fully upgraded or not the best that you can make.