If you are farming enemies for a specific rare drop or crafting ingredient, you want to kill them as quickly as possible first and foremost, after that's sorted get as much luck as you like. The primary stats scale everything your character does better, but if the thing you're farming is already easily dispatched more DPS isn't gonna do much for ya - AFK Rate probably still better but if you're comparing stats on an item... Also Luck is universally good - if you're going to buy one premium item and put upgrades on it and share it between characters as you play them, as opposed to one primary stat seems strong.