Do you remeber anything more? As those archers can had quite a bit of valour and/or your FMAA can have been exhausted or worse.

Exhaution makes a serious difference. I often use a desert corp that lacks armour and they have a heavy tendency to loose the first wave while winning the rest (when exhaustion has striked).

Expert gives a 30% combatbonus= about 1 valour and +4 morale, while hard gives a 15% bonus, but 1 valour is a far cry from making an archer being able to match FMAA.

Being severely outstared is a much bigger problem.