I really like your last list. I love all the singing spears too. I would probably drop the heat lances on the Reavers though as you are probably going to do more turboboosting/jinking/assaulting then shooting. Might want to drop one unit of scourges and with the points saved from the lost heat lances on the bikes you could take a second flyer to give you more anti-tank... Crimson Hunter exarch or preferably the Nightwing (from imperial armor aeuronautica, double bright lances, double shuriken cannons, 2+ jink save)