At what point do the escorts get down right nasty?

[MarkShot]

I am playing my first GWX2 career. It's close to the end of 1941. I was wondering at what point do the escort become a serious threat following an attack on a convoy?

So far, I have attacked convoys with 5-6 escorts. The escorts have done an acceptable job of picking up a submerged sub and from time to time forcing it deep and thus achieving a mission kill.

However, I haven't found them posing a real challenge to elude. So, I was wondering when does this change?

I am not finding much team work. Generally, maybe one or two of them will be near and drop DCs, but I haven't had to worry about all of them forming a tight circle and boxing me in.

For me, I tend to find the portion of WWII sub games where after an attack you have been detected submerged either actively or passively, the most challenging aspect of the game. (assuming they have gotten contact) The two key problems of first breaking contact and second disengaging are great deal of fun. Typically, when you are looking at 5 or more escorts, it can become extremely challenging.

So, that's what I am wondering about. When do the detection equipment, accuracy of the attack, quality of the tactics, and number of escorts reach truly "hands shaking" proportions?

Thanks.