That is the point exactly! Even ATR pilots can't mesure the size of dropplets!
It was not a ATR problem, but a weather problem. Other a/c in the same situation could have suffered the same fate.
American Eagle pilots got extensive training in identifying ice problem areas in the aftermath of this accident. Bytheway; the ATR has a excellent ice detection system onboard. In addition the boots are extended farther back on the wingcord as a result of the accident.
I bet new modifications has and will be done to the new generation Q400. Look at the B737. It would have been dead decades ago if it had'n been for the modifications.