according to what they said yesterday, the probelm is that there's such a long run from the pit exit lights to the end of the pit exit lane that given the high speeds at that point its almost impossible for a team or marshalls to judge if a car will arrive at the corner before during or after another exits the end of the exit lane. add in the poor rear mirror vision and a car in the exit lane can't see a car on the racing line. what also may have saved hamilton is that when he saw buemi, he didn't panic and lock his brakes on cold tyres and slide into the middle of the bend but went as far to the inside as possible, if buemi hadn't gone up the escape lane, he was left room to make it through the bend though obviously he would have lost time.
untill they change the rules to do something about the mirrors probably the only solution is an extra flag / signal marshall towards the end of the pit exit lane to signal if a car is close, though once again its a hard thing to judge