I've found that 3 Affliction rate up effects (maxed accessories) + Mordred's Affliction resist down debuff nearly guarantees that character debuffs land on neutral element. Naturally, that's what I'm stacking on all my debuffers. This effect is so strong it's even worth building a team around--that is, ensuring that all ATK/DEF debuffs you need are covered by characters rather than your Soul. Coincidentally, that's also a requirement for a good Bishujorin Burst build, which will soon be highly desirable for Rank 4 Accessory Quests.