Well, been reading this thread for a couple of... what? weeks?.. seen the arguments of both sides. One side is elitist jerks who are happy to have their special snowflakes. Another is general baddies, who are not raiding because Blizz give normal raids for first side. It is very funny, but know this. While you are arguing who is who, it somehow became almost impossible to find a raider if your raider somehow is absent today. It is a Wednesday, clean CD, we have a Large populated server, and after yelling for an hour in /4 noone wants to raid. We have a medium (11 normal) progress, and all we needed was a decently (490+) geared Hunter, even with absolutely NO experience in boss kills. We just wanted a fast clear farm run. We got nothing.
Lets take the situation to a new grade. Lets assume we lost our 10th raider for ever, and we need a replacement. With such a situation over people don't want to be bothered with raiding higher that lfr slack we possibly won't find any replacement. And, voila - I'm quite sure at least 7 of us won't leave for another guild, we'll just switch to pvp/whatever.
That is where your raiders gone. Its simple, really. T15 normal raids are not hard, they are exhausting over any possible limits. Even in LFR. You do realise the difference between "hard" and "exhausting"? If not, I'll tell you. Exhausting is when you kill Durumu at 14th pull but NOONE in your raid actually feels like he wants to continue raiding today. Exhausting is when you kill Tortos on 4th pull, but your healers ask to end raid today because they are just overtired and want to rest. Do you really think that exhausting equals hard? Well, if you do, and if you love to feel like you've carried all day bags with sand after your raid is over, I'm glad for you. But don't think that majority of players want the same.
People play game to relax and enjoy group play, its that easy. If people are forced to carry bags full of sand instead of enjoying group play, they leave. And that is where your raiders are now.
Going to solutions how to fix this. The number of boss' mechanics should be decreased in a way boss not becomes a sensory overload shitstorm with a 2x a4 list of abilities to remember. Next. Raid moving on every boss MUST BE decreased at least for five times/or give every caster the ability to cast while moving. It is not a light athletics championship, we're here to kill Azeroth's sworn enemies, not for a running contest. Next. Every thing said before must be applied ONLY to normal modes, heroic modes are nice as they are for the people who do them.
ps. And freaking god damn, let paladins' bubble and all alike abilities to cheese over oneshot mechanics, it is ridiculous when your bubble protects you from every damage in the game, except these 100000000 boss' oneshot abilities.