Foz: Your observations are correct. I had quite similar experiences.
There is also another problem though and that happens if the routers are very few in number or at least one of your chasers overtakes the routers. In those cases your chasers tend to stop, regroup and never get anywhere chasing them.
Further problem is if the routing unit is nearing the end of the map. Then your chasers often for some weird reason go either left or right of the routers, run against the edge of the map and then against the routers by which time they will have left the battlefield.