Well I have over the months saved up duplicate Eddies and I do use them in Gauntlet - I have not sharded many dupe Eds but I have used my duplicates when I can in the earlier rounds - I have done the same with several allies too. I have only got to top 50 and Grand Master II SSS once or maybe twice I think so cant remember what you can and cannot use but pretty sure a full roster and dupes will give you those sorts of numbers.