When I say individual popularity, I mean an extreme disparity between their popularity and the combined popularity of the group. Yoona & SNSD don't count because of the reason above etc. The only instance I can think of were an individual member's popularity helped the group is Hani & Exid.
Im Siwan & Hyunsik - ZE:A
Kyungri - 9 Muses
It really seems to hurt a group more than help, but I guess once a company decides a group has no more potential to grow, the put all their resources behind the member that has the most popularity