Neji and Sasuke S

But in Neji's skill description says that it doesn't reduces affliction damage... It's confusing bro

I think it's better to consider affliction damage as being a unique type of damage. That would prevents misinterpretations and facilitate understanding

Neji skill says that it deals 5 less damage with non-affliction class skills, not that it makes they deal 5 less non-affliction damage. Affliction Class is one thing, Affliction Damage is other thing, Sasuke S skill is Chakra Class, so its not Affliction Class, so it's reduced.

It is already split, class is not the same as damage, there is no Piercing Class and Piercing Damage isn't associated with any class; in the same way, Affliction Damage isn't related with any specific class at all, there literaly can be a Physical Class skill that deals Affliction Damage, just like Physical Class skills can do normal, piercing, bleeding... Affliction Class skills can also do normal, piercing, bleeding damage, classes aren't linked with damage types at all.