I pretty much only use OR on Defense now my fifth is usually GK, as he has a similar function- taunt and cleanse. group hug should double as a heal when the dots land. retribution means more heals and outgoing damage.
that's the theory, anyway. JKR was fine with Hoda or Old Ben in GK's spot (usually Hoda) I'm gonna have to switch it up once padme returns.
Other 5th's I can think of- Vader (heal + big hit, decently tough toon, especially with his unique zeta), Wampa (obv reasons), Rex/Chirrut/AA (if they don't have their teams, cleanse + ten up/hot/bonus turn would be nice), maybe even gamorrean gaurd, and of course other general plugs like Nest
