Don't push toons to r7 if you don't have to. Most work pretty much as well at r4 as they do at r7. Lots work just fine at g13. Save your relic materials for the GL requirements. They suddenly get super scarce after your second GL.
There is no need to make a super powered arena team any more. Make a bunch of good teams for GAC. You can pick your battles in GAC, so there is no need to try and out match mirrors with high relics. Use good counters and low or no relics are fine.
Sith empire teams benefit from being all sith empire. HK and marauder are a good pair to add. I also like to put SET in that team to save malak for a solo in GAC.
Bring up some empire to be with vader and palp. Shore trooper is like Vader's best bud.