Dorain trained four days a week. He worked hard and he trained intensely. But I don't think he was the hardest worker if it is measured by time spent in the gym and other ancillary work. Jay Cutler trained twice a day six days a week. Countless across the world are in the gym six days a week in addition to hold a full time job.
I've seen many train more intensely. Platz for one. Look at some of the routines Milos does and puts his clients through?
But, unlike what we are told and what people like and want to believe, the hardest worker is rarely, if ever, the most successful. It's the smartest and most gifted. Dorian was very meticulous in his training and didn't just willy nilly go through a workout. He kept written records and charted his progress or lack thereof and constantly made adjustments. Same with hormones and diet. Dorian was genetically gifted like they all are at the pro level but I don't think he was the most gifted. One of the things that separated him from the pack wasn't just his size, their were guys like Dillet and Nasser that matched him there, it was his conditioning. And that requires not only supreme discipline by knowing your body to a T.