World of Warcraft is and always has been the king of casual MMOs. At no point in it's life can you consider it a "hardcore" MMO. Play something that came before WoW and you'll see what hardcore ends up being. There is a reason it became so popular: It was easy. Though yes, the Warcraft/Blizzard name didn't hurt it.
I do love the people saying TBC was the more hardcore era of the game and how perfect it was. I'm just going to point out that the term "welfare epics" (which I see TBC lovers complaining about so often) started in TBC.