You will ALWAYS have losses versus a NPC lvl 6 and above thanks to giving them trebuchets. No way around that. Acceptable losses perhaps but that is up to you.
And it's not "odd" in the least if you understand how game combat mechanics work. At Arch 9/HBR 6 your balls were going too fast and getting you into range of the AT's too quickly. You want your range to outpace your speed and closing distance for balls to be effective, at least until you hit Archery 10. At that point, it no longer matters (well not in this example anyways).

