Turians don't have any sort of natural protection from their metallic skin-thing. It's only for radiation. From the ME wiki:
Shouldn't krogans get some sort of blood rage ability too? Something like a barbarian's rage when they get below a certain amount of hp.Their reflective plate-like skin makes turians less susceptible to long-term, low-level radiation exposure, but they do not possess any sort of 'natural armor'.
On an unrelated note, I would find the Star Wars Saga Edition a better fit for Mass Effect. Force powers changed to biotics and it's almost done, with a possible few powers which need their fluff rewritten. Tech "powers" still need to be done though.