Hi Dontcareanymore,
Every viva is different and I can't tell you what to expect. However, I don't know anyone who failed with decent data chapters. The data chapeters are the "meat" of your thesis and if they are solid you thesis is likely passable. I wouldn't worry too much about your intro or formatting because fixing them would be definition of corrections in my opinion. Revise and resubmit or straight fail is if your results/methodology/conclusions have severe flaws and don't constitute a contribution to your field.
Goodluck!