I'd have to think about that, but you're probably right. It's not missing essential tracks on the level of Hanger Management, Chutes and Matter, etc
It's not missing large setpieces, but as Jason suggests it is missing much of the connective tissue that holds everything together. In no way is the album a cohesive listening experience or a rounded presentation of the score.
Also some unused bars put in an appearance, such as the contrapuntal treatment of all the ring themes at Mount Doom. I would not suggest getting worked up over any of the missing material - it's pretty inconsequential.
Hopefully things will start moving and this thing will happen at Radio City - it would be a tragedy not to complete the trilogy there!