With a bit of practice you should be able to solo the lamps as a blade dancer, just have invisibility maximised, don't touch me's help a lot as well. Run past the first lamp and stab a thrall on the way through to go invis, when you get to the second lamp stoop until invis (weight of darkness should go to zero as well), then stoop at each lamp until invis & zero weight of darkness then move onto the next & do the same. When you get to the final lamp & bridge, set it off and use your super but press r2 (I think), to go invis. Make your way to behind the final lamp to a large rock, stoop there until the lamp explodes and you go invis again, then jump on top of the small rock next to the lamp. The thralls won't be able to touch you and you should be able to shoot the ogre easily, then just wait there until the bridge forms. Good luck!