according to wowprogress, 7030 guilds have cleared the first 3 on mythic while 15816 have done the same feat on heroic. that's 140,000 players for mythic and between 158,160 and 474,480 players who do heroic. they don't keep stats on normal but I am sure you could add another 2-300 thousand quite easily (probably more), and then you have the people who do LFR which again would be quite significant. but sure, let's remove raiding altogether and wave goodbye to hundreds of thousands of subs, possibly millions