Proposing an In Game System Idea

These make great stories, and work well in single-player games but when you come down to the practical matter of it, they can quickly become un-fun things one has to grind for peak performance, particularly if the effects are strong.

I don't want to hear from a raid group "Okay, everyone grind your poison resistance by next Saturday. We're taking on the poison dragon next."

As that anime showed, this mainly leads to OP shit. And as Song said, everyone will just require their guild members to grind out any possible passives, especially if they are permanent.