Team advice needed

BillyBeans

Right now in arena, I take #1 pretty much daily at payout time. I usually fall to no lower than 15 with the occasional drop to 20ish or not dropping outside of top 5.

I run
Dooku lead
Daka (gear 9)
Rey
QGJ (gear 9)
GS (gear 9)

All 7*

I am thinking of putting in either ST Han or RG. Han is 7* and gear 8. RG is 5* and gear 9.

Here is my question...

Should I not try to fix something that is not broke? Or can I avoid the drop to 20ish every once in a while using one of my tanks. If I use a tank, who do they replace?

Thanks y'all!