Game Mechanics: More than 4 npc's shouldn't be able to attack a target at once

[Sarius]

No proof of this, but I believe it was either late Kunark or Velious. If a target had more than 4 mobs agroed, as the 5th plus mobs approached melee range, that would run away and not engage until one of the original 4 was downed. I think this is where "quad" kiting came from.