NEW YORK (Bloomberg) — Willis Group Holdings Ltd., the world’s third-largest insurance broker, was sued for gender bias by a former vice-president who says women were paid less than men and denied high-profile assignments and promotions.Adrianne Cronas’s lawsuit, filed yesterday in Manhattan federal courts, accuses London-based Willis of a “pattern and practice of sex discrimination.” The suit seeks class action, or group, status on behalf of women who worked at or above the level of assistant vice-president.