One way to deal with archers is to not chase them, but fall back.
Retreat into some bushes with a soldier or two and fall further back with the rest of your team.
The archer will come looking for your troops if he cannot see any, and then you can ambush them with your hidden units.
The ranged units of the enemy will only retreat if they see you getting nearby.
Plague Rats - we're not famous, but we get the job done.