2 warm up sets, 2 moderate to heavy, one 'working' set to failure.
for big muscles like the lats he might do an isolation exercise first like the nautilus machine to fatigue the lats as its so much stronger than say the arms or forearms.
Are you saying that's what you do? Putting your spin of Dorian's one warm-up set, one moderate set, and one set to absolute failure?
For the legs, he did start with an isolation exercise. In this case, leg extension before going to the 45 degree leg press, and ending with the standing Hack squat. When the subject of barbell squats came up, as they always do when talking about leg training, he said he stopped doing barbell squats back in 1988. Three years before he competed in his first Mr. Olympia in 1991.
As you mentioned, he did the same for back. I wonder why not for chest? He seem to start with the incline barbell. So did Mentzer when you look at his later training videos.
Pre-exhaust for the legs and back but not for the chest.