The declines are because raider.io is toxic.
People running say a 10 key want people with 800+ raider.io. But to get 800 io, you need an average of a successful 10 key in every mythic dungeon. And to get a successful 10 key in every dungeon, you need to run keys of 10 or higher. But to run a key of 10 or higher you need 800+ io.
So its a casual player trap where you will never have the io to get an invite to do the type of keys you want.
"First thing that crosses my mind: I didn't get any GameFAQs Karma yesterday." Math Murderer after getting his appendix removed.