First: dedicated archer is a pointless thing, because there are enemies in game that are nearly immune to ranged damage and there are enemies that will slaughter back line characters.
Second: As soon as i am able, i tend to start recruiting backgrounds with both high melee and at least ~50 ranged skill at level 1. Usually its raiders. As i start getting such characters, i pretty much start increasing the number of people who carry ranged weapons as secondary. So ultimately i end up with 12 people who can fire a bolt or 2 worth of crossbow bolts (usually crossbows) in order to soften up enemies. Sometimes ill keep 2 bowmen to pick off enemy ranged units.
When it comes to second line people (6 in front 6 in the back) they tend to be primarily armed with 2 handed weapons with 2 reach (usually great axe or whatever its called nowdays). As secondary, if their ranged is at least 50, i give them either a crossbow or a bow. Their use is rather obvious; start unloading damage at range and keep doing that until your melee weapon is needed.
The second line people usually wear lighter armors (specially early on) because they dont really get engaged. It is crucial to get some levels and that skill that allow you to walk out of enemy’s range (whatever its called i forgot) before you start fighting things like Orc Warriors that can push your people back and reach the second line people.