TW defense is Arena worthiness... Just with more forced options because you can only fill up so many slots with meta teams, and then you move to the next meta. Just saying.... don't get mad that everyone uses arena worthiness as a baseline and then ask for how a character does in arena styled battles...
That being said I have seen many arena videos of RJT, R2, BB-8, L3, and T3 doing extremely well. I'm not sure how well it would do on defense as the videos are always on offense. Have also seen IPD in there for L3 but that's definitely an offensive squad.