Stat Priority is
Base Damage
Max Discipline
RCR
Bonus % damage
Area Damage (this because it rolls to 24% on weapons)
Vit
You don't want CDR on your weapon. Even though it rolls to 10% it doesn't help over another slot because you will still need 2 other slot.
This the way the list works. You want the first 4 for a good weapon. If the weapon doesn't have one of the first 4 roll for it to be added. RCR is always there and cannot be rerolled but you can add. Don't do that.
What it comes down to is you will either have Vit or Area Damage as your last priority. You want AD but the other stats are more important. If you don't have max discipline the weapon is garbage. But increasing weapon damage is more important than increasing Max Discipline from a lower roll.
Weapon damage is what all your other bonuses multiply. You want something close to 3400 dps without IAS.
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Good call, night stalker is particularly well suited to a fire build. Great ammy.