TC, it is a good and important post, but I'd like to add to it in a different dimension.
"Trigger control" has become a default answer when somebody raises concerns of distance shooting accuracy. I personally have spent a considerable amount of time on wall drill, b&d drills, balancing brass drill trying to get respectable 25 yard groups.
Then I noticed that my long distance groups are better when I shoot at 3x5 cards rather than conventional bullseye.
Then I noticed that my groups are 40-50% better when I use pistol-mounted RDS vs. irons-equipped slide on the same frame. Obviously, RDS won't do much for my trigger control or shot anticipation directly.
What both of these things - 3x5 card and RDS - offered me was a consistent shot-to-shot sight picture, which in my case appears to as important, and may be even more important, that trigger control.
Folks who are stuck at suboptimal long range groups need to look at all aspects of marksmanship to diagnose their problems. Change of targets, use of alternative sighting systems and external observation are very helpful here.