i personally wouldn't work with 90+% of 1rm on deads and squats in the same workout, much less twice a week. i guess you can try it and see if you start overtraining at which point you can do a deloading phase of lower intensity training for a week. if you insist on DL'ing and squatting in the same workout, work one strength component with deads (ie absolute strength) and another facet of strength with the squats (strength-endurance, speed-strength w/e) or vice versa, that might be just enough to keep you from overtraining.