See, I think this is one of the points where people always clash; levelling and end-game. Levelling in WoW has indeed become incredibly easy, I'll give you that. But a large group of players see the actual game as all the stuff that happens after you reach max level.
So yes, by your definition, WoW is easy, but seen by the players that see end-game as the actual game, it is not. And no, if you say it isn't hard, either you haven't played it for years, or you have a super-hardcore guild that can actually kill everything on heroic without breaking a sweat. There aren't a lot of those guilds around.
About quest quality, for something else entirely, try giving The Secret World a try. The questing/levelling experience is very nice, with nice story, plot and atmosphere. The end-game is incredibly boring and grindy after a while, though, so you might not want to get too much into that. It's also incredibly buggy in some areas.