in all fairness i think the beginning of the end was mop.
i always say that the term "mop hero" was not invented by chance. cataclysm saw some subs drop, but there was still the feeling of "community" and reputation on realms or battlegroups. there was drama amongst pvpers. it was actually possible to outplay the enemy and do something about it. yes you had triple dps, or RLS with rogue having legendaries and warlock with firelands staff and cunning trinket from dragon soul. more shit ensued as well. nothing was ever balanced, it was just more fun (maybe slightly worse than wotlk?).
i'll give you few examples:
1 - in Cataclysm instant roots did not exist. when a boomkin had to roots+beam me, he needed to bait my hand of freedom, or press solar beam quickly enough before i maybe instantly cleansed myself after the roots landed on my character. Now you have instant roots and instant solar beam. skill, hello? my skill and the boomkin's are irrelevant now.
2 - Cleanse cooldown. IT KILLED THE GAME. could i cleanse myself if roots weren't instant? NO CAUSE THEN I CANNOT CLEANSE THE POLYMORPH or whatever else. cleansing added a huge depth to a healer's skill. in MoP it got to the point where you couldn't cleanse polymorphs but had to save it for the frost bomb because that was what took 60% of your hp. cool i guess, that's not scripted right?
3 - in Season 12, which was MoP season 1, I literally remember shadowpriest - warrior - resto shamans popping out of nowhere. people who literally had challenger and maybe rival accross wotlk and cataclysm. I faced this team with my multi glad Cataclysm team mates and even if we won, there was nothing to do: they could have been shit, but CHARGE STUN + SHADOW PRIEST SILENCE on the healer = guaranteed kill / trinket / bubble or whatever. just NO CHANCE OF OUTPLAYING THEM WITHOUT MAJOR CDS!
in Cataclysm you could still outheal a full enemy's cds by playing better. lately, if I don't use wings as soon as a feral druid uses incarnation, as in, if i'm a fool and try to outplay him for 10 seconds, he'll still force me to use them sooner or later. this means there will eventually be a point where he uses incarnation again and my wings aren't ready yet because i've used them too late when he FIRST used incarnation.
it's funny how we spend time typing here for absolutely no reason, but it just feels like the solution is at hand all the time but they're too stupid to actually apply it. increase overall healing and overall dps for everyone. make wings or dps cds increase throughput by MAX 10/20%. Game is almost fixed.
edit: damn AJ not showing full helmets :S