The system probably works fine for JP players. I hear mana datacenter has 72-player frontlines battles all day.
For whatever reason, most of the English community shunned pvp almost as much as they shunned the diadem.
Even if queue times were reduced by abolishing GC restrictions, we would keep being matched with the same people over and over due to small community. So I think participation is the biggest problem of all, and I've seen multiple people say they quit pvp after a bad experience of harassment.