My Sith Marauder is Light II and he's just almost balanced, he fought in a compasionate way all way through but is hard to say: most of the choices of the Dark Side weakens the Sith Empire in one way or another, YET he's more alive than most of the Jedi.
On the other hand something curious happened with my Sith Assassin: I desired her to be a Dark Side Agent of Chaos [she's Dark II], but eventually it came like ice when just before I finished her 3rd Chapter and I wanted to advance faster so I began the Makeb Story Line:
On the Ship
So I began looking after what I have done, just to give you an idea of what my Sith Lady has done:
I believe the Sith Empire is not evil at all, but they just are fighting for their very survival and the worst enemy of them is NOT the Jedi or the chaotic Republic of fools; but the "tradition" is what the Empire has to overcome: infighting that will last until Darth Bane...
The Empire is doomed, but I still like it better than the Republic!