Tzero, I'm not entirely sure that passives are available, however I'm still at or around the same level of understanding you are, probably.
Though I seem to have a problem of my own that I'd appreciate help with if anyone could get a grip around my situation. It seems that some of my powers simply do not activate anymore.
The details are as follows:
1) Cain tripmine, Nightshade blades, Recon mine, siege Pulse, and hex shield do not seem to appear when turning on the powers.
2) I know siege pulse and hex shield used to work, because I had them on a separate single player file.
3) I have had a fresh install since that other file was completed, however I saved the parts requiring editing in the walk through and later replaced the fresh files with them. To me, this means that everything should still work.... that doesn't appear to be the case.
4) When I say that those powers do not "work" I mean that they simply do not appear at all in my list when I'm turning on the MP powers. Not sure if that specification slims down the issue or not, but there it is.
Hope that helps someone figure out the issue, because I'm a little wary of editing anything myself.