I'll take that advice to the point on how to deadlift to the point since you seem to know what you're talking about. Also that guy in the vid is INSANE, 405 KILOS? Holy crap! i'll be happy if i can even lift a 100 kilos in my lifetime hehehe
If you commit yourself to deadlifting (for instance twice a week: one day working on technique with lighter weights, and one day going to max weights) - you'll find that you'll probably lift 100 kgs within a few months.
The body quickly adapts to deadlifting, and gains are fast (at first - up to the 150 - 200 kg point).
What you are really be training is your central nervous system (you can think of it as the computer which activates muscles). The more you deadlift, the better your CNS becomes at recruiting muscles. So gains are NOT completely based on muscle growth. Although muscle growth will occur (and especially so with the deadlift), a big part of the training is simply learning how to be STRONG (in other words how to squeeze the maximum level of strength out of your body).
People often say 'isnt that bad for your back' or 'that doesnt look healthy', but they are uneducated on the issue. With proper technique, the deadlift is a safe exercise, and it is based on a primitive movement: bending down to pick up a large object, something our species has been doing for a long time. Sitting at a computer for 8 hours a day is bad for your back. Deadlifting will make you stand up straight, strengthening your posterior chain.