I've fed them as a staple insect for adults for over 15 years now. They are severely limited as they are very fattening. We are talking around 10 a week at max. This number provides s good amount of protein, and fat for an adult dragon. Fat is necessary in the diet, it just shouldn't be over done.
I wouldn't feed them as a staple to a growing dragon as its protein needs would force way too much fat into the diet if superworms only were used.
I do also use smaller superworms with younger dragons, but my younger dragons get a mix usually of 3-5 different insects, and they aren't the bulk of the feeder.
-Brandon