It's easy to design a better system than dailies, pump out infinite amounts of content, it's just not feasible to pull off. Some people want to spend more time in the game than others, maybe even every day, and we want to make sure they have something to do. While we'd love for that to be fresh and unique content every time, it's simply not feasible. Thus, dailies. Give people something to do each time they log in (if they choose to do so every day).
Not to toot the Mists of Pandaria horn too hard, but I think our general zone design, daily, and scenario approach is pretty solid. Part of what makes dailies a bit tedious, aside from being tedious, is the rewards are desired but may not always quite fit the time investment. I see quite a bit of that being solved and making sure if you're logging in to do some dailies or scenarios, you feel like you made a good chunk of progress toward advancing your character.
I don't think feasibility should be the cardinal, over-arching reason for implementing content. That approach has worked fine for Blizzard in the past (granted), but it won't work so well with this new generation of MMO players.
In opening BGs, then Dungeons, and now Raids to the Random Finder tool, Blizzard has trended the game away from the world itself to the "quasi-world" inbetween servers (the place you go when you queue for RDF).
You have more access to me that this kind of information - but i'd guess that players spend the bulk of their playtime inside the random-finder "quasi-world" than they do the world-itself. Sure, "dailies" provides an incentive to play around in the world-itself, but that isn't "fun" per se - it's seen as a "grind" to something fun, or something neat.
The world is incredibly important to an MMO, and as such, I think that Blizzard Dev. team should be far more concerned with improving the world in which we play, rather than the quasi-world where rampant abuse and poor social manners are rewarded.
Per example - while I wasn't too fond of EQ2 (I played it for all of 4 months), they had the right idea; make the WORLD "come alive." As you progressed in level, NPCs interacted with you in different ways, and through such interactivity SoE was able to increase the "immersiveness" of the game.
In Mythic's Warhammer Age of Reckoning, they added 'achievement statues' to the capital cities, so if you are a player who is 'top' on your server (in your class) for Renown, kills, quests (etc), then you get a statue placed in the city in your liking - such things add to the value of the world itself.
Dailies are all fine and well for giving players an incentive to get out of the cities and go forth into the world of warcraft - but when those are done, they return to the quasi-world of the Random Finder; and i've got to say, thats a HUGE waste of such a large world which ends up function, in the end, as mere wallpaper.