Did u ever think that when you stated "In all the "Top guilds" I have been in, whenever I wanted to bring a holy priest I got laughed at, it's been like this for years.", it is not because holy priest sucks, it is because you suck? Also, those "best guilds" you were in, they were up when ICC and rest instances were hella broken - easier than this day. It didn't matter what healer you bring, even 5 ret could heal LK 25heroic.
But i sort of agree with you about "classes being viable", since mostly DPS is about gear and mostly performance. Also every raid enviroment are different, so can't make that big conclusions about rankings from "recount/skada" -meters.