if i wear a evil druid card then khalizt is useless?
whats the best armor a BS can wear for niffing?
Now, THAT is up to you

disguise is good if you run a high vit/str build, which is always reccommended. Silence prevents the monsters from using their attacks and spells.
Garm is used too, in highly overupped def. armor. Used in conjunction with Defense gear. The more defense you have, the less damage the monsters normal attacks will do, naturally.
Evil Druid is a good one too. It prevents Stone curse and one other effect from niff, I forget which one. However, with Evil Druid, if you die, you cannot be ress'd, and you cannot be healed while wearing it.
Bathory is the alternative to ED if you're looking into preventing shadow attacks full power. With Bathory, you can be healed and ressed, but Bathory is an SQI ingredient, and may be expensive.
People will also use other status armors randomy, IE poisoning armor, because a poisioned monster takes more damage from normal attacks, and etc. Up to you ;3