As far as I can see, they have all the requirements - they generally pop up out of nowhere, are lvl 30 and look quite threatening.
In reality, their actual function seems to be to die very quickly whilst making slightly sad noises. Every time a group pops, they seem to me to be saying "Oh noes" in a slightly Tellytubbyish way, as if they know what's about to happen. I almost feel sorry for them