You've already gotten plenty of solid feedback from some of the usual suspects, and given that I'm just a regular guy with a 505 deadlift, I don't consider myself much of an authority. I found this article ("What We Mortals Can Learn From Eddie Hall's Deadlift") helpful. In particular, it helped me understand the "hips rising too fast" thing a little better.
Pay particular heed to the discussion of people who take a deep squat position at the start, and how that actually relates to proper hip position when the pull really begins. Some people think that you have to "get low" at the start of a deadlift, but you shouldn't confuse "getting low" with really getting into proper hip position.
I also think that you might consider wearing your belt a little higher. That was a big a-ha for me, learning what the "real" purpose of a belt in a deadlift is. Once I started wearing my belt a little higher up, I felt like I could really brace my core HARD against the belt, and that really gave me more confidence that I was getting ALL of my body into the pull.