The end game quests that give 580 weapons seem to be a very poorly designed portion of the game. The quests are long and interesting, but the problem is giving access to such a strong weapons before defensive gear has the chance to catch up. This tilts the game dramatically in the favor of doing damage, and imbalances gameplay in general due to that. If your weapons are all 580, but your armor is all still low 500s, then in pvp, it warps intended balance poorly in one direction.
I think the rewards for these quest lines should be toned down dramatically, maybe even to being just slightly better than faction gear.