As far as Sastasha homework, all that's really needed is to learn your role. For lancer, this means understanding your skills and working out a rotation to use. Not 100% certain on this, but this will likely involve starting off with Heavy Thrust for the buff (preferably do it from the monster's side for bonus damage), then spam Impulse Drive from behind (This will actually do more damage than your True Thrust + Vorpal Thrust, which is 150 + 200 potency over two turns, or average 175 potency per turn, while Impulse Drive is straight up 180 potency per attack). Put Heavy Thrust back up whenever your buff falls off, use Leg Sweep periodically for damage (On some mobs you may wish to avoid using stunning moves so they can be stunned to interrupt certain moves. No monsters really require this in Sastasha), and you should be golden. I wouldn't really worry about Feint, it can reduce damage dealt to the tank, but the healer should be more than capable of keeping the tank up and DPSing without the enfeeble.

Naturally, your rotation will change as you level up and learn new skills. Of particular note, damage over time abilities like Phlebotomize at level 30 should be kept up whenever possible (Unless the mob is close to death), as they basically function as your most powerful attacks once all the damage has been dealt from it.