imo, the game just looks and feels dated.
Compare it to all the more recent games, what's WoW missing? - it looks OLD .. but is it the vintage kind of old wine feel to you? or is it more like old people's home old feel?
imo, do a WoW 2, wrap up this one in the next 2-3 years and relaunch the game and this time with an engine they can upgrade.. a more long term vision.
I'm not sure if any amount of tweaking would make a difference... do you know of anything blizzard could do to attract your friends that quit?