Suggestion - make vault more fun!
The vault gives the same thing every time - a few helpful but totally boring wildcards. The first time I earned a vault I was excited, but when I saw what was in it I totally stopped caring about them.
Suggestion: Add something to the vault that is specific and fun! In addition to the wildcards given, you could also earn 3 random cosmetics and 1 random pack of cards from an older format. Anything to make it not just winning a blank canvas. Maybe a chance to win a draft token or event entry or something.
Note for potential naysayers: I am not saying that they should give any less wildcards - those are very helpful and an important part of the Arena economy. I'm suggesting they add something that also adds a little fun (and costs them nothing).