From: Alberta, Canada
That is exactly my point. Temporarily detaching from the convoy and patrolling just ahead of the main body is one thing. In game terms (if I understand correctly), this would just be the assumed role of the escorts in the (same) TF. I would imagine that the escorts in a TF aren't moving side by side with the transports. Some would be a bit out ahead, scouting things out. (Some would be traveling more or less along side while one maybe bringing up the rear.) So, I would think that the game incorporates such techniques into its concept of "escort".
By creating a separate TF to move 46 miles ahead of the transports you've created a very different situation. Did detached DDs operate that far ahead of the main body? I suspect it may have been more like 5 miles or less. Any further ahead and the sub just dives, waits a bit and returns toward the surface to intercept the following ships.
My point is, by sending the single DD TF ahead, you've gone from patrolling to baiting (getting the sub to waste torpedoes and its concealment status).
From what I've read, detached escorts could spend hours hunting individual contacts and end up hundreds of miles away from the convoy at times, requiring hours to close the distance. Later in the war when the Allies could put actual hunting groups together made up of escorts they did just that, essentially ranged ahead of a convoy and attacked any submarine contacts, and continued to attack until contact was lost or they were needed to close the distance back to the Convoy. You mention a range of 5-6 miles, but you also realize a hex is 40 nautical miles, so theoretically these DD's could range many miles ahead of the TF following.
I honestly don't think the tactic is in any way gamey. A single DD may not always raise the DL enough to prevent a successful submarine attack on the follow up TF. In fact, in my PBEM, I can launch a DC attack against an Allied sub in the am phase and it then targets the same TF or a follow up TF in the PM phase. I'm not trying to discount your opinion or thoughts here, but personally I see no problem with this tactic. As Chickenboy and I have mentioned, it happened in real life and I think kudos to anyone who is able apply that to the game.
To each their own, and as before, if you feel that strongly against the tactic just be clear with your opponent and institute a house rule to eliminate the problem. then it's all good.
Luck is the residue of design - John Milton
Don't mistake lack of talent for genius - Peter Steele (Type O Negative)