Finally got my fourth key today. Played all the events. I get why they seemed to want to spin it out but I think there would have been more effective ways to do it. Now, the fact that I have all 4 keys puts the onus on me for not having the new characters (because I apparently suck at the challenges). I'd much rather the onus be on me, too. Because, before I didn't have the new characters because I was flat out denied the opportunity to have them. (Thanks RNGesus.) I just don't think it's cool that a percentage of the player base is completely denied the opportunity to access the trials.