but there must be a time when there is no choice and a pilot has to take the decision to avoid a CB regardless and then inform ATC what is going to do because he/she has to and has no options for safety even if ATC it is going to be too difficult to route.. is that a common happening?
it does happen but it would be nice if we got told. Unlike a certain pilot who's first call was "turning right 20 degrees to avoid" across the nose of the parallel heading traffic 5 miles to his right!