I *always* put my archers in front of my spears / swords. But I don't rely on the "skirmish"-mode to pull them to safety - I pull them out myself when I judge they are in peril.

When the AI deploys in front of the line, well - they get the benefit of the extra range, and as I'm playing on expert and as a blitzer, I rarely have the ability (ie numbers and/or quality) to make the AI army rout from hitting the line head on. It takes a little more "preparation".

/KotR