i agree. its probably a technique or lack thereof thing.
although i know when you're classically trained, there are some notes where your jaw will invariably move, especially with high notes (tho prolly higher than shoshana's end note). this is because the magnitude of the sound is so powerful, your jaw invariably shakes. this is also the reason for real vibratto i think, but im not sure.
however this is probably not the case with shoshana, by listening to her voice.
as for the "gooeeewwdd", lol. one thing shoshana is able to do really well is to change the intensity and character of certain notes. there are MANY ways to do this, depending on what you want, and one is to articulate certain ways to let the sound carry better in the way she wants it to. unfortunately it lacks aesthetic visual qualities.
i also agree on the "for good" bit. i did not enjoy that at all when i saw it. but it may have been just that performance.
ps. TONS of things are pre-recorded on broadway. most of christine's really high notes (think c's and e's) in phantom are pre-recorded, to protect the soprano singing them. this doesnt mean she can't sing them, but its just better than having her do it every day of the week or whatever, and leaving one more soprano w/o a voice. i doubt defying gravity's G's and F's are pre-recorded, they're too low and you would be able to tell at any rate if they were from the audience, because there'd be a change in volume. the notes that ARE prerecorded in wicked (or should be, anyway), are glinda's for the same reason as mentioned above.
Tenme por lo que soy, por lo que puedo ser, y si te importo hoy, tenme nena, o vete!