I developed and playtested the 68 campaign, so yes, I have played it and used the Mk16. To successfully use it, you have to fire it at WW2-like ranges, often within 2000 yards, and use spreads. It is the escorts that can detect your torpedoes, and if they do, they will warn all other ships which then take evasive action. There's a pattern to the convoy's movements, and you need to observe them to figure it out. Also some escorts will be performing sprint and drift routines, which is probably what you refer to as erratic maneuvering.
That said, there's a bug in the current version where subs share the datalink and can detect your weapons, then warn the convoy, but this is being fixed, as well as rebalancing the sensors and weapons to improve gameplay.
The ships are indeed more manueverable than they should be, but this is likely because turns no longer induce drag (which they used to). Once we put that back in they'll behave more realistically.
If you visit
this site, you can clearly see the turning circle remains the same but the turn speed deteriorates as speed is lost during the turn.