Your chances of getting a legendary out of 72 shards with a dropchance of 0,8% (double the normal drop Chance): 44%

Your chances of getting 5 void Champions out of 72 shards with a dropchance of 12% (double the normal drop Chance): 54%

statatistics and rng im afraid :/

Rng is same for everyone and it is fine. Problem is that you have possibility to spend unlimited amount of money to get eventually what you want.

I have 3 legendary champs after three months of play 

all three came from blue shards