I don't think JTR is unseating CLS necessarily because she's better, but because people want a change. She can certainly make the offensive a little easier. But CLS, Raid Han, Thrawn, GK, R2 is still a solid team. Like leef said, trying to use him as plugged in anywhere he's not as good, but then again I never saw him as OP on defense as Raid Han anyway. But if the team is right, he's not going anywhere.
Nightsisters can also contend in a JTR arena because most JTR teams have no tenacity up and no group healing.