The tricky aspect of wholesale lending (lending to corporates) is that the shit does not hit the roof until skeletons are out in the open. This is not about Yes Bank but general comment.
There are several cases in point. I will point to the most talked about recent event. Suddenly there are so many Jewellery / Diamond defaults / frauds that have come up in last 2 months. Did they turn fraud in few days? Did the management not know?
There is also another aspect which is known as ever-greening. That primarily refers to process of restructuring to keep stressed loans non-delinquent. RBI expects reporting on these so as to classify them as impaired. But, there are ways where it was noticed earlier that banks could circumvent to avoid NPA issues.
Hence, corporate lending is not easy, losses are chunky and it does not appear that the system is very transparent.
Thus, the mitigant in Indian context is not % NPA or provision coverage or comfort of risk management system. The only comfort is authenticity of management and robustness of risk culture. Take your pick.
Else, one fine day RBI will come down heavily to clean the system and then skeletons can not be hidden. This can happen tomorrow or 5 years down the line but then why take that risk?