I'm prolly gonna piss somebody off with this response but I don't care and I'm not gonna sugar coat it.
When I see guys use several variations of the deadlift that don't include full ROM, I just feel that they are lazy. Rack pulls are a bullshit lift in my opinion. It simulates nothing in a real deadlift. Its all Ego. I used to do these a lot and they never got me anywhere. What the hell did an 800+ rack pull equal? A mid six pull. Wow it really didn't help my pull at all.
If you want to get better at the pull, then pull from the floor. You can still do partial movements but always start from the floor. Hell the weight will be lighter but you can jack up the intensity. This is where reps come into play. Quit being lazy.
Some people claim that they can't pull from the floor week in and week out. Well me neither. I pull 3 out of every 4 weeks and each week is a different intensity/set/rep scheme. Going heavy all of the time is stupid. I think pulling more than once a week is stupid as well. You gotta be smart about it and quit being lazy.