Yup!

Something to be share by me is

if you happen to collect ( if not, do so...maybe there will be event of summoning champion which will help boost the reward meter ) Green Mystery Shard while grind for exp in Campaign or other mode in the game,

Summon it one by one. Yup One by one. ( Click those 500 silver summon button one after another )

If you get 10 shard, you can just summon all of them at once ( there will be button for that ) which I always do before and end up getting more common and uncommon champion. No Rare Champion ( 3 star ) at all. Usually get only 2 Uncommon ( 2 star ) and most were common ( 1 star ).

When I summon one by one, it seem I get higher chance of getting Rare champion ( 3 star ) or more uncommon champion ( 2 star )...

I know, it's random. I just lucky. Fine but still it's what happen to me and...

maybe it will do so to you. I'm just saying...