I'm in August 1942 in my first attempt at a full campaign and the game itself is going fine, but I have only lost three subs to date - now I believe the US actually lost around 50 in the real war, a loss rate of about one a month from December 1941 to September 1945.
Just wondering from anyone who has completed a campaign, I assume the losses increase in WP2 and WP3 with the default ASWs of +1 and +2 but did you find that you lost few boats at the start and a roughly correct amount towards the end?
One of the main causes of loss is encounters with Diligent Escorts. WP1 only has one DE in the D cup, but then WP2 gets another in the C cup and from WP3 on another in the B cup. This will make a *big* difference to your loss rate.
The chance of transit events giving a 'Lost at Sea' result rises sharply after WP1, and of course, as your torpedoes improve the chances of being sunk by your own Circular Running Torpedo increase.
You'll see losses increase quickly once you leave WP1!