Myself and a number of players are tracking the drop rates. Currently I’m at 1 in 23 for a band gnome but I expect this to change as we get more data.
If anyone is interested in being part of the data tracking team, we are collecting information on the drop chances in the vault. The more data we have, the better our estimates will be.
Very simple process, click the link, request access to the Google sheet , I will then set you up your own tab and mail you back to say access has been granted. Scroll down to the tab that has your name on it and then enter in the rewards you got from each key.