Diane Seaman may have one of the toughest jobs in corporate America.

Ms. Seaman is the chief actuary for WellPoint Inc., the insurer which projects to enroll more than 600,000 in the new health care exchanges—likely the most for any insurer. It's her job to develop rates for dozens of different offerings around the country. But for people who thrive on information, these can be harrowing times.

The...