part of the issue is that all units in a formation follow the same logic. if you stick your infantry into any of the "tight" formations they slow down. this includes those troops reinforcing your lines from all the way across the map. its also what leads troops to get caught on eachother when you tell them to assume shield wall formation exposing their back as they endlessly attempt to crawl their way to their new assigned position. troops told to assume a specific location should always run to get to it as fast as they can unless some other condition is met like enemy troop within x units or projectile came within x units recently.