Each point of expertise(not rating) reduces the chance for your attack to be dodged, blocked, or parried by 0.25% in both PvE and PvP. Keep in mind that parry and block only work if the defender is facing the attacker, while dodge works regardless of facing. So to some degree, the average solo player is going to have a different opinion of the value of Expertise in both PVE and PVP compared to a multi-boxer, they do not share the same positioning limitations we have.

HTH