best thus far for me atleast, the biggest shock was the number of dailies available each day, as someone who did rarely spend 2 hours doing dailies in cata it was a shock to spend something like 4-5 hours on dailies( i am not exaggerating, might be the disorganized way i do the quests so i end up flying all over the continent ) in terms of ratings
pvp: N/A since i don't pvp
pve: seems fairly balanced for 5 mans atleast can't say much in regards to raids since the only bosses i've done is Sha of anger, Galleon and Feng the Accursed but from my experience with those three it seems fairly well balanced so it will be a 8/10 mainly due to my inexperience in Mogu'shan vaults.
PvE difficulty: i'd say 8-9/10 the dungeons aren't as facerollable as the Wotlk ones from my experiences but they aren't quite as hard the Cata ones before nerfs as for the raiding i found on Feng the accursed atleast that there is a small margin for errors ( fx. people not moving from lightning fist or standing in fire which can lead to mana issues for the healers in the last phase) let alone how fast arcane resonance can fuck you over during 3rd phase.
the story i give a 10/10 because for me the story have been the most gripping for any expansion thus far.
overall a solid 9/10