While you might be able to get away with a G11+4 or 5 on JTR and BB8, RT and Scav Rey must be G12. Their health pools are too small at G11 to absorb a drain force and direct attack from DN. So you would need a ton of RNG in your favor to make them last long enough to post above 2%. R2 not only has to be G12, but also have the multi-tool because otherwise his health steal is simply too little to recover any meaningful health.
Unfortunately, for HSTR the answer is always "G12 +0" minimum, but if you get a run with RNG on your side I'd probably say: JTR G11+5, BB8 G11+5, R2 G12+multi-tool, RT G12+medpac, Scav Rey G12 could get you 2%. Maybe.
Running Visas (with her zeta) in place of R2 might help you get away with a little less, but not much. If you're a couple months out from attempted HSTR I'd recommend farming that. She's a relatively easy gear.