I spread my chasing unit (usually a light horse) into 2 rows, set on loose formation before ordering them to chase the routing unit. It seems to help a bit, at least the chasing unit changes directions smoother (less of that colliding with it's neighbour and coming to a dead stop problem)

What really gets on my nerves is when the chasing unit comes to a dead stop just before it comes into contact with the routing unit. I've had it happen a few times particularly with General's Bodyguards.