Environment!
You nailed the story-telling, I think some parts are excellent.
You nailed the music, obviously.
You nailed the special effect sounds.
You nailed the art.
But I'm not immersed because I'm playing on a painting. No movement in the sky, no changing weather patterns, or going light to dark.
I hate to bring up the elephant in the room. But I was a serious WoW player for 5 years. A big part of what sucked me in was the feeling of immersion from the changing environment.
Seeing areas from different perspectives.
I've leveled a trooper to 50 and am not leveling a JK in the low 30s and the game is 3 months old. It just doesn't feel live and I'm not drawn to it like the elephant.
Not leaving yet, just disappointed.