Well my experience is that there's a lot of variance in their skill levels even later on in the war, and the sea state has a huge effect as well. For a case in point I refer to my last patrol, in that my 1st sinking during the gig was achieved after succeeding in sneaking into a convoy from the front flank with the point escort cluelessly passing me at 500yds... or less! And this in early 1943 in foul weather...
But _then_ I also encountered a lone DD with an ace complex in good(ish) weather later when cruising on the U.S Eastern Seaboard waters near New York. The bugger was sharp as a tack and fast; I crash-dove and started manouvering, but he nevertheless acquired a solid contact and kept it, making my job of shaking him a very tedious one indeed! Took me 3 hours and a depth of 254m(!) to finally get in the clear
So yep, they do come in various levels of having a clue even after 1942 IMHO.