Hi all, 

I have been playing this game now for roughly 6 months, reached level 60, doing most dungeons on 14 or 15. I'm a F2P kind of guy and enjoy the game this way. 

I have NO Legendaries, a few good epics - Royal Guard, Gorgorab, Jareg and the normal rares that most other people also have - the starter heroes and Apoth. No good Void champs. 

I would suggest to at least not always have really crappy odds of getting a "good" champion, that you build in an increased percentage of getting a rare hero every time I open a green shard, increased percentage of getting an epic and legendary when opening a blue shard and same for void and yellow shards. 

So basically it would look like this:

Base % of getting a rare champion from opening a green shard is 1,4% - with each green shard I open and do not get a rare champion that number increases by 0,5% or so. When I finally receive a rare champion, the bonus % resets to 1,4% again. 

And then apply a % increase for epics and legendaries for blue, purple and yellow crystals.

Just my thoughts. Let me know yours.