I think it's about time Kabam addressed the 6* dupe issue
Traditionally, when you dupe a champ, you get shards for the next star tier up.
We don't have 7* champs in the game hence no 7* shards.
At the moment, when you dupe a 6* you get levels on the sig ability, in some cases sig level scaling is critical and in other not so much. It would be nice on top of those sig levels and iso to get some shards. Even 275 6* shards would be better than nothing (but more would make more sense).
The humongous elephant in the room is duping a max sig 6*. It is literally worse than duping a 4*. You've basically flushed 10,000 6* shards (maybe even 13k or 15k) down the toilet.
I don't have a max sig 6* yet, but I've seen other people's effort amount to nothing. It's pretty disheartening.