I feel the same. With IRAI mod and destroyers tracking you down harder, the sonarman is not enough precise. You just dont know what is coming on you and you take a lot of depth charge too close.
I think the sensor is OK but the refresh time is not. A sonar contact takes too much time to get updated, so for destroyers it is a big problem since the closest destroyer will run over you and the sonar contact hasnt been refreshed.
A "Focus on destroyer" mod would be great for the sonarman, high refresh rate on destroyers so we can guess wich one is going for a depth charge run... and avoid it !