I agree with you when it comes to using a woolly bugger. I also used to use small live crays for browns in my pre-flyfishing days.
I was in a Crayfish pattern swap with a bunch of other guys who fished bass etc. (I don't) and every one of the twelve patterns came back with claws, so I have to believe that there is some merit in them. Even large crays molt and are eaten.
I am restricted to having only fished for trout with them.