Getting Champions Shards from Chests. . . .

I have every champ, been that way for a while. The last 2 chests I've opened, meaning after collecting 6 keys, I've gotten Evelynn and now Sion.

I understand giving only skins is 'too generous', but getting champions is SUCH a let down, ESPECIALLY WHEN YOU ALREADY OWN THEM!

Could there be a system where if you own that champion, the chances of rolling said champion is reduced?? If you don't own the champ it makes sense, but constantly getting champs I've had for years is sooo unsatisfying.