All scrapper combos are good, SR is just SR, meshes well with everything: great defense, defdebuff resistance, scaling resistances, nice recharge boost in quickness.
The goal is 45% for melee, ranged and aoe if you want to be softcapped.
Don't expect to dodge a lot of stuff before SOs though, SR is quite fragile till 22.
Don't see any guides on this combo. Is this a good combo? I know the spines/fire-dark combos throw down more damage, but I am looking for somthing a little tougher. What is the goal for positional defense 45%, 50%?