binding NPCs to other NPCs

[ChaosSlayerZ]

too bad we don't have eq2 style "npc packs"
but walking in formation most likely achieved by giving those npcs very precise walking grids. But those grids do not hold for very long - with slightest interruption- like momentary agro - their perfect walk pattern will be broken.
You could do it very tricky way, where you continuously check along the walk grid that all npcs are at appropriate position before continuing to the next grid point, and tell them to stop and wait if necessary, while others catch up.