If your rear is shot, it's hard to tell if it is REALLY coming from the rear or not. Only around corners when your RATB's are REALLY shot will you be able to really tell if it's your rear toe.
I could tell last night when it was doing the crab dance at a stop light, but I already knew they were torn to bits anyways. They make a big difference, a degree of toe is much more noticeable than you think.