Custom Battle Algorithm

[Armor Nick]

In my project, my characters will have low stats (5-20), and I need to customize the battle algorithms in order to be able to have this. Now, I played around with attack_effect so far, and I've come up with this:

  def attack_effect(attacker)
    # Clear critical flag
    self.critical = false
    # First hit detection
    hit_result = (rand(50) < attacker.hit)
    # If hit occurs
    if hit_result == true
      # Calculate basic damage
      atk = [attacker.atk + 50, 0].max
      self.damage = atk * (attacker.str)
      # Element correction
      self.damage *= elements_correct(attacker.element_set)
      # If damage value is strictly positive
      if self.damage > 0
        # Critical correction
        if rand(100) < 4 * attacker.agi / self.agi + critical_bonus(attacker)
          self.damage += (((attacker.atk + 30) * (attacker.str + 30) * self.pdef) / ((self.pdef + 70) * (self.pdef + 50)))
          self.damage *= 9 / 7
          self.critical = true
        end
        # Guard correction
        if self.guarding?
          self.damage = guard_effect(self.damage)
        end
      end
      # Second hit detection
      hit_result = (rand(50) < rand(attacker.agi))
    end
    # If hit occurs
    if hit_result == true
      # State Removed by Shock
      remove_states_shock
      # Substract damage from HP
      self.hp -= self.damage
      # State change
      @state_changed = false
      states_plus(attacker.plus_state_set)
      states_minus(attacker.minus_state_set)
    # When missing
    else
      # Set damage to "Miss"
      self.damage = "Miss"
      # Clear critical flag
      self.critical = false
    end
    # End Method
    return true
  end

The problem is that the damage I get is too high. Can anyone tell me what's wrong and how I would fix this?

Thanks in advance.