Still have the stuff we came up with a few years back?
How about a survival tree that focuses on removing harmful debuffs. Kind of like a cloak of Shadows if your familiar with world of warcraft at all. I'm not super familiar with the various debuffs of this game. But maybe as you progress further up the tree it could include more things it works against and maybe lessen it's cool down time. I would think something like that could add a layer to the strategy element.
I was just going to look at those versions of the game because it would be easiest to implement probably and im not very creative with my ideas. Jedi kind of have a cloak of shadows with its heal states and full heal self. Would be cool to see a type of CoB skill for the defensive branch. My suggestion for offensive power skills is harder hitting skills, faster abilities, and maybe being able to move and cast when you max out that tree.