Troop drop rate when using gem keys seems broken

Platform, device version and operating system
Xbox One, since latest update

What you were expecting to happen, and what actually happened
Used 50 Event keys 2 days ago (3rd May) in an attempt to get the mythic (Champion Of Anu) from the event kingdom. From those 50 keys I received 41 copies of the current glory reward troop (Vanguard). If this isn’t a glitch then event keys are now worth the same or less than glory keys completely devaluing them and distorting all reward tiers in all facets of the game

How often does this happen? When did it begin happening?
It happened once for me as I didn’t want to waste more keys but I know that it happened to at least one of my guildmates as well. I believe it may have started after the new patch (3.4) as I have not heard of it happening before

Event keys only give you 1 in 1000 chase for mythic.

Its not a bug, it works as intended.