Really? That's what you call a passive ability that all Forsaken have?
I asked for lore to back up your argument. I'm not going to take these claims to be true just because you say so.Really so Dk's suffer horrible miserable pain that radiates their entire body, each and every waking moment of their pitiful existence? There is no lore to indicate they suffer pain each waking moment, we encounter various undead who suffer from insanity, and lack emotion in general, but the feeling of actual pain is rather special.
A quick skim of banshee lore on WoWpedia shows nothing along the lines of "suffer horrible pain 24/7 flowing throughout their whole bodies", just that snippet from earlier that says their suffering was brought on by being given awareness which is something all Forsaken have.