I'm around where you are now with my Assassin, and went Darkness as well. You won't do as much burst, but overall, I just feel that being able to stay alive a bit longer makes up for it. And force pull rocks in both Voidstar and Huttball. If the ball carrier is in your court, jump off the ledge and pull the carrier down with you
Will end up going full Darkness I think, with a few points in Madness.