Ack is doing what is is supposed to do IMHO.
I have never seen it continue "20 miles away".
It is basically a barrage of shrapnell that is exploded at your altitude (or near it), and the intent is for you to fly through it and take damage. Works pretty much like it is supposed to.
If it had to be manned in order to work, we would never see carrier groups. They would all be sunk as they spawned, as they would have very little protection. (How many would devote thier time in AH to manning them on a CV?)
As far as the lethality of it, don't hang around in the middle of it.
Get in, get the job done and get out. In other words, you pays your dollar, you takes your chances.
I have no problems with it. I have been killed by it and have flown through it unscathed. It adds a bit of "pucker factor" to the sortie.
Cheers,
RTR