There can be other explanations to this problem. First off, are you sure your form is correct even lifting moderate weight? It should be the case that you should be able to keep pretty solid form until you get to maybe 85% of max and probably even higher for some people.
If you cant maintain solid form on lower weight than when your form really craps out maximally, which it will with anyone, you will really be in some deep shit. Also, what is your programming like?
Poliquin has an older article talking about leg days and he has a terrific approach. Every 5 days working on a leg exercise and trying to drive your strength up in a given exercise. For instance you could squat one day, then 5 days later work on your split squats, then 5 days later work on your deadlift.
It is amazing how long you can stay away from a certain lift and maintain or even increase strength. I have been trying this and it has been working superbly. My deadlift felt great yesterday and I hadnt deadlifted in two weeks. The longer break in between will give your shins a chance to recover so you dont just keep ripping open the same cuts.
Another trick I used to use that helped with the bar is obviously wear athletic pants. That is the only way to go. Another trick I used to use is spraying my pants with WD-40. Cuts down on the friction to the point where the lift goes like butter, it almost slides down your leg too easily at first.
Not sure if WD-40 is a great thing to get into your cuts, but it never bothered me… That might be another idea for you… But whatever you do dont ditch the standard deads…