Vaan and Penelo do actually get enough screentime, but it's a different type.
You can see them in the background, acting like buffoons. I found this out because, during most of the cutscenes, if Baru-Sama isn't there, I tend to drive my eyes away from the main focus and enjoy the scenery.

Of course, you probably wouldn't even want to THINK about watching those two when they aren't in the foreground. They certainly do act their age.

As for the story length, I remember stating three times that it was BIG. First by looking at the size of the most detailed official walkthrough to date, next by seeing the background goings-on, and then by looking at my playtime and noticing it maxed out everything else I've ever played (except for X-2, but that's only because I kept having to start over after beating it the 100th time or so and going after another unaccomplished goal. )

I'm happy with XII. In fact, I think it's a new favorite.