I remember coming across and article by Bob Gaynor on the deadlift. Not a great article in terms of readability and I wouldn't want to emulate his technique but then again I can't and probably never will pull that much and I'm twenty years his junior. But one thing that he was adamant on - or against I should say - is the idea that you should not deadlift to get better at deadlifting.
People that say this invariably cite a few examples of lifters that have made big increases in their deadlift while doing everything but deadlifting. Basically anecdotal. Bob said if you want a big deadlift you have to deadlift your ass off and I couldn't agree more. He said that he has always deadlifted at least once per week (when he has trained for competition and at all other times during training).
There are very few lifters who get a decent deadlift without deadlifting a lot!