Assaulting Massilia, I had a strange experience with my Camillan triarii. Two units of them, each with 2 silver chevrons, went onto the walls from siege towers. The Greek defenders were placed on other parts of the wall, so the triarii went right at them, soon smashing into two units of massiliotai hoplitai with just one bronze chevron. I had great confidence in my veteran triarii, but then something strange happened. The triarii weren't winning. The fight stayed very close, but in the end it was my triarii that were destroyed to the last man, although there were only very few of the defending hoplites alive.

How is that outcome possible? I was so surprised I went to take a look at the stats, and the massaliotai (who were using their spears) have the same lethality and mass, so the huge difference in defense and attack should have made the difference for my triarii. I don't get it