Climbing in arena without Revan, Traya, or C-3PO

Top 20 is highly unlikely without having any of those toons. To stay in top 100 and perhaps break into top 50, I'd run something like CLS, Chewy, Han, Thrawn and Nest (or perhaps R2 could find a place in that team). Your sith are decent, but they would be an easy target without Traya. Rebels hold better, at least in my experience.
I'm still running Traya until I finish gearing Revan and I prefer to target Revan teams instead of rebels, even if they don't have C3.