Nah man, usually 3 and sometimes 4 work sets per exercise, but I only do 1 exercise per body part, so it end up being 3 or 4 work sets per body part. For example, on Incline I keep the weight the same for each work set, then when I can complete 3 or 4 sets for 4 reps I bump up da weight for my next workout.
Yeah man, those 4 reps are to failure or very near failure, and I train rather frequently, and I train to failure or near failure on ALL my work sets.
Remember... What it all boils down to is the practice of PROGRESSIVE OVERLOAD and it doesn't really matter HOW you practice it, just as long as your training style allows you to practice it. And for me, this style works best in allowing me to apply PROGRESSIVE OVERLOAD 
I rest 3 or 4 min btw sets. I'm not trying to chase "the pump" I'm trying to chase "granite-like" muscle density
these are all really good training methods. the bolded part about going to failure i disagree with, because personally i get much better results by staying underneath failure. i stay stronger longer and am able to push more total weight. failure causing alot of fatigue and buuild up of acid in me. maybe your different. but id suggest you try it out, if you havent. (staying a couple reps shy of failure).
the part i made big, thats the most important part. your right. so if going to failure works best for you then keep doing it. i think you might get better results in terms of being able ot gain strength and sized as well by staying shy of failure. one thing though, having very short training sessions willnot be optimal. right now it works good for you because your going to failure and that puts a limit on how many sets you can do before your strength drops and your overtraining. when you stay shy of fialure you can do alot more sets with the same weight before you become fatigued.
the 3-4 minute rest between sets is very good. bodybuilders always train fast and they are very mistaken for doing so so. its about total tonnage first and foremost.
one thing i would say is that you should definitely incorporate higher rep training, not just for your lower body. sticking to reps below 4 is great for building up strength and size too, and i really like the method you use (i do the same thing), however you are missing out on alow of good stuff that comes from higher reps (like 8-12 range) if your not doing them. again, these sets wouldnt be to failure. they would be after your heavy sets, with about 50% or so of what you were using in the heavy sets, and youd just do 2-3 (althoguh you could do more) sets of higher reps. this will pump up your muscles real nice, help with recovery, stimulate some finbers you wouldnt have stimulated otherwise, booost your metabolism, boost your glyocgen stores, maybe help with fascia stretchgin, and increase the number of satellite cells as well. all that scientific mumbo jumbo aside-youll grow better and look better by adding in some high rep sets in addition to your heavy sets.
all in all i can tell you know how to train.
just smy 2 cents..
