Looking at next year, one thing cannot be overlooked. Petra has done horribly this year on virtually all mandatory events, and yet, somehow still managed to end the year close to top 50 (assuming she doesn't make a series of huge upsets here and wins the title). Correct me if I'm wrong, but I think all these events are mandatory: AO, Doha, IW, Miami, Madrid, Wimbledon, USO, Beijing - in neither of these tournaments has she managed to get away with a win. Hope that changes next year.
You make an excellent point, ma re. Her points from the mandatories have been a big drag on her ranking. That situation will improve next year--if only because it can't get any worse!
Btw, I think there are only 8 mandatories: the four GS's, the two mini-GS's (IW, Miami) and Madrid and Beijing.