Yea, sure, millions of players will kill mythic Azhara. Think again, if they didn't nerf KJ, Ghun, Jaina there would be like 700 guilds with a kill. Nerfing bosses opens the chance for the "millions" more like 1000 guilds with a 25 player roster, do the math, 25k. 50k, if being very very generous and saying there will be 2k guilds killing if before next content release. You really didn't even thought about it, yea?
If they didn't nerf it at all on the other hand.. we are looking at what? 10k players? guestimation.