I think it would be a huge mistake for a lot of guys. If there is one thing about Dorian's style I disagree with, it is that he only did 2 warm-up sets before his max working set of 5-8 reps, even when it was his first exercise for that bodypart.
For example, when using 475 lb on decline bench press (he has done as much as 500 X 5 on that exercise, at his strongest) and only doing 2 warm-ups, you have to make huge weight jumps in order to reach 500 lbs by your 3rd set.
Sorry, but when using that much weight for such low reps, 2 warm-up sets is insufficient. Assuming he started with 135 lbs, what would he weight progression look like? Maybe something like this?
135 X 20, 315 X 12, 500 X 5.
Even if he stated at 225 lbs, what is he going to do next? 400 lbs? Anyway you look at it, no matter what progression scheme you use, 2 warm-ups is not enough to safely work your way up to 500 lbs lbs on the bench press. I would venture to say that this may be one of the reasons why Dorian tore so many muscles. Dorian himself said that his injuries were not the result of a lapse in technique, but due to years of wear and tear on his connective tissue.
Is it any coincidence that connective tissue is damaged more easily in the absence of sufficient warm-ups? The muscles, joints, connective tissue, and nervous system all need to be "prepared" before the body can safely handle heavy weights to failure. Being properly warmed up entails a rise in muscle temperature, filling the muscles with blood (you don't need to have a super pump, but they should be at least mildly to moderately pumped), and stretching the muscles out through the range of motion you will be training in, as well as preparing the nervous system for the heavy weights to come.
The stronger and older you get, the more warm-ups your body requires in order to avoid injury. Even when I use 405 for bench press, my weight progression goes as follows:
Bar X 20-30
135 X 20
185 X 15
225 X 12
275 X 8-10
315 X 8-10
365 X 3-4
405 X failure
...and sometimes I even do a second set with 135 lbs. I am not even slightly tired by the time I reach my work-set, as none of my warm-ups are difficult, but my body and mind feel ready to handle max weight to failure.
I couldn't imagine using 100 lbs more and only doing 2 warm-ups. That is just an injury waiting to happen.
Ok and how about the second exercise? If you allready fully warmed up after decline press then i guess you dont need more than one or two warm ups if any right?