But come on you'd have to agree that heroic/scenario farm + LFR as it is right now can only be discribed as "fun" for an extremely small part of the playerbase. Most people that I know that don't raid are unsubbed right now.
So after Cata the game suddenly got old. Cata by itself was extremely easy after the first raid tier (with the exception of heroic rag). The subs still kept dropping. Remember that they came up with the annual pass and D3 just to keep people subbed into DS? Arguably the easiest and worst raid (granted not just because of the difficulty and LFR but still) in Cata.
Edit:
Idk why people are so hooked up on the dungeon heroics argument. Blizzard fixed their mistake in the 3/5 department in MoP. They just switched the tagging from normal/heroic to heroic/challenge (notice how there aren't any normals anymore?).
Also arguably the new heroic scenarios are just as hard as Cata heroics if you tackle them without raid gear.