How could your archer die in first round? It takes at last 2 turns for orcs to get to your line. Young ones tend to arrive first so they delay contact with warriors usually further. And it would take another turn for warrior to break through your lines to get to your archers.
Did you charge your line forward to get the high ground?
Anyway, engaging 5 orc warriors on day 80 isn’t good idea, unless you’re well equipped, have very good brothers and you are already familiar with orc warriors and what they can do. That means 300 armors, 2H weapons, ideally including few 2H warhamers, couple of billhooks and few nets. And your brothers should have 80+ melee attack and 20+ melee defense with high end perks. At last most of them. That way you could expect to win that fight without loosing somebody. Anything less and it’s up to some luck.
Loosing like this is however part of the game and why it is so much fun. It’s part of the challenge. Most of us got owned when we first encountered orc warriors. Just like when we have encountered other high end enemies. Every enemy in the game uses specific fighting stile and have specific strengths and weaknesses. Nothing can prepare you for such first time encounter.