I suggest adding ranged units to this quest that can harass targets from afar.
If the animated stargazer hunters should be doing this, then their script is bugged.
There are ranged units, and those do. Sounds like a bug to me akin to orcs unequipping weapons.
I've only gone on this quest once but I definitely remember being attacked by headless animated stargazers with shortbows. I did notice, however, that if you engage them in melee combat, they'll pull out a club and start wailing on you. I've never seen, however, a headless animated stargazer switch from club back to their shortbow.
They don't use the shortbows. Either they have no ammo, or they lack a script to let them use it, or they prefer their clubs.