Gear 9 works for me... Four stars as well. I'll be gear10 in the next couple weeks. (But I'm only level 80.) Finish in the top 30 on average, it depends on your squad and your shard.
Depends on how tough your leader board is. If you leave him at 4* you're going to to want to be at gear x or xi with serious mods to be a serious bad as.
I've been running him at g9 4* since I got him a couple months ago and stay top 50 most of the time and most of that time I ran the same squad you are using.
There was a huge leap in viability at g10 for me. That and 5 stars made it so g11 wiggs could no longer down him in one shot. Maul, tfp and palpy come in and mop them up after Biggs' op special.
Mine is gear 10 and 5*, and holds his own well. Not quite ready to replace my droid team in my arena yet though. I'll probably throw them in and move mods over once I get Bobba to T11. Just need 25 more of those Mk7 Shield generators.
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Good luck.