I think I have just identified a bug with these guys - they periodically cast a pretty well no save death (death saves don't work) spell on you every so often, but they give it away with an animation allowing you to run out of range. The bug is in that if you knock them down, the knock down animation masks the casting animation but doesn't stop them casting - so you get no warning. Tried it again - the text doesn't appear when this happens either
