i deadlifted w legs for the longest time and realized two things: (1) squatting and leg pressing only exhausted my muscles to the max, so i wasnt achieving the ideal benefits of deadlifting for my lower back. (2) the added strain of another heavy compound exercise only taxed my legs and i never really experienced much growth size-wise.
for a few weeks i tried supersetting heavy squats with heavy deadlifts. i would do something like, warm-up squat 135 then immediately deadlift 135...up to squatting 405 then deadlifting 315. it only made me nauseous and i didnt get as many reps as i had hoped to.
then i made the decision to deadlift only on back days cause deadlifts primarily target your lower back and also incorporate upper back (my upper back is ALWAYS sore after a good deadlift routine). bearing this in mind, doing deadlifts on leg day then doing back on another day is just overtraining your upper back. needless to say, i can squat a lot more on leg days bc i have more energy and deadlift a helluva lot more on back days for the same reason.