Best defensive combo with JTR/BB8/R2/GK

Still testing a lot these myself and I'm liking the added droid synergy with Chopper. I'm trying K2 instead of GK but GK's cleanse and group attack seem better than an additional 8% speed from another droid.

Edit: K2 is dead weight, not good at all

I want the answer to be Chopper, since gearing him makes my phoenix better for tb/tw and he's a crew member. OB, chopper and Srey are all pretty hefty gear commitments to get arena-ready, so I want to choose wisely.

If the answer is not ScRey, I'm not sure why. Her ability to destroy people with flurry is the awesome. The best defense sometimes is a good offense.