Hi Darkevil
archers provide supporting fire IF there is a garrison to kill off.
when the defenses are only made up of Tower Defenses, that's when early-game armies of light troops are the most vulnerable
no easy solution : you need to boost your starting Morale and increase your wall-breaking damage output
for the starting Morale, I gave you a few tips before
for wall-breaking, you need to use swordsmen and rams :
1) raise your Combat Techs (Attack to do more melee damage and Armor to have higher resistance for all troops)
2) and remember that you can use melee troops up to 3x time the base garrison of the enemy fort (say you want to break a fort 3, base garrison 200, then you can use up to 600 swordsmen each round)
when you combine both elements, it should be a much easier job to perform
Have fun,