I don’t always get a legendary drop, but when I do it is a multiple of a card I already have. After getting Kerberos for the third time, I decided to make a team out of all three. This is the result of a match where the first enemy was killed with skulls, a lucky orb filled all three Kerberos, and each one devoured the remaining enemies in a row.
There is someone who has a defense team made up of 4 Kerberos 
I’m not sure how to feel about that. On one hand, my team is more practical. On the other, he has one more Kerberos than I do. 
You know you’ll get a fourth one. It is an unwritten rule of Gems of War: once you have a legendary you’ll keep getting it 
Yeah, You’re right, Mekalthi. I got Gorgotha more than 20 times. Even from an iron key.
Purchasing 40 magic keys for 5 times, and I always got him.
Dangerous strategy 