It is designed to capture the will, rather than just making it so the vampire can't harm you. Like taking control of both body and soul. He would still be himself, but he would be unable to deny his master anything. In a normal bond, the vampire can't leave the master, or hurt them, and the invasive bond makes it so that the vampire doesn't even WANT to leave them. He can still argue and disagree with the human, he just ends up submitting out of instinct. I see the seven doses take quite a while to administer, and in between a lot of tension, drama, and interplay.