How about when you open a legendary token you get a choice of two or three covers to pick from? That way you improve your chances of getting a cover you do not have. I am getting to the stage where I have a lot of four star heroes covered in one colour but not in other colours. A lot of 5/1/2 etc. This way If you can choose from a couple different covers.
SInce vaulting, i have huge problem with duplicates both from legendaries and heroics… not mentioning my 0/5/0 Goblin… 1 of 3… hell, even 1 of 2 would be cool.