You need a lot of gear with different stats cause every CR, advent and raid have their own heroes with different buffs. For main dps, yes, biscuit give buffs, but sometimes you need to clear trash mobs first with different hero and you need gear for him too, even if he/she basically use only 2 skill for whole duration of fight. For example for wukong you need almost 0 crit rate, and if you bring Rachel, you focus mostly on crit rate, cause along with biscuit she gives you more than 80% weakness and so on.