Cassie is a very high dmg champion standalone, not counting the use of her 30% increase combos. I find myself rolling constantly to get that dmg increase out and keep hitting my targets. A neat chain move I found (and obliterated a Drogoz with) is using disengage to knock an enemy up, roll backwards (forward if you're feeling 180 flashy) and shoot the disengaged enemy while airborne. It was a very hard hit against Drogoz that I was able to clean up in one more hit while he tried to thrust away. The chained combo does 60% more damage to the target and is a move that will make someone back off to get to safety. I use Incitement III to get as many rolls as I can out. A good practice is to go to the shooting range or even against bots and get used to shooting immediately after rolling and being sure you can hit 80% of your shots to be effective. Lunge II is there so if someone tries to run away I can flag them down or if I need to create distance I can roll backwards or to the side and split. Quiver II is a preference pick. I'd rather have the 2 extra arrows rather than to find myself hindered by 2 seconds with a reload in a gunfight. Somersault II for those moments where you're losing a gunfight or being pushed and need to get away immediately.
All decks created are player preference and are by no means guaranteed to work for everyone. Give it a test, let me know what you think. See you in the realm.
*EDIT*: Somersault II replaced with Life Drain II due to overall beneficial load out.