Ok, well I went with Madness actually to try it out. I was worried that I would be a bit of a glass cannon, but that has not been the case at all. I use Khem to tank, get him geared up in decent greens and it does the trick. I have some limited CC, specced into Oppressive Force and Haunted Dreams for some adds and it seems to work well. Much less stand there and slug away, but there is more movement and tactical use of powers. If I get in trouble I can stealth out and quickly return to finish off my foes, which seems much more assassin-y to me. I have to say madness is a fun spec, hope it continues to be good. I even seem to take out elites just as well. Khem dies sometimes against elites, but I was able to take elites 1-2 levels above me. The only time I had problems with them was if the elites had the ability to put Khem to sleep and focus on me. But even those went down when i got my stun rotations working ok.
Thank you to the others who replied, although most responses say go darkness, I appreciate the feedback all the same.