Well, I don't know about the bristleworms, but I detest the asterina stars. The small ones that I find grazing on algae either on the glass or on the rock are fine. But the moment I see a big one fully enveloping the head of a zoa that was perfectly happy the day before, he is out of the tank faster than you can say "low-down dirty varmint".
(When I see an asterina, I have caught myself saying "I keel you!". Jeff Dunham fans will understand what I mean)
Regarding big bristleworms, I wonder what food source they have in order to reach that size anyway?