They are good enough, working often on decently strong or simply troublesome monsters [cats, minotaur mages, great water dragon]... I think there's no need to beef them up

I don't know if anything changed in the pre releases but I've stunned the ACW with a blessed stun wand before.

I have too in 1.1.1, but I couldn't get it to work in p9.

ACW seems to have been buffed resistance-wise lately, but I never really found him that problematic.

Maybe cause of my tendency to soften him up with a PoCC

Stun rays don't seem to follow the usual chances for bolt-shrugging as other spells. Monsters like kobolds, orcs and cats seem to shrug them off too often in comparison with regular spells - I've had cats ignore them several times in a row, which never happens with fire bolts, for instance. I think that's what Andur wants to change here, and in that case, I agree.

I've rarely ever seen it stun anything more powerful than a rat... Which is pointless to stun.

Very valid point - agreed and voted on :)

I believe that part of the problem with stun ray effectiveness is that it gets a double check. First, the monster can dodge the ray, and second, the monster can resist the ray. So it's actually somewhat lower probability of hitting than other bolt spells, and much more sensitive to luck and casting attributes.