I have many customers that have done just that. I myself made the switch from BeefHeart as my main food to Freeze Dried Black Worms. Freeze Dried Black Worms have an excellent nutritional profile. They are high in protein and fats and so well taken by fish thats there is little waste food left in the tank, making it a cleaner food than Beefheart mixes, some of which can be very messy. I don't think there is anything wrong with feeding Discus Beefheart or pellets.
I am not an advocate for feeding discus anyone one kind of food solely though some do so with great success. I think a varied Diet is a more natural diet for a fish.
Best always,
Al