Thank you BKL—this is the clearest explanation I've seen yet of how Tactical Advantage works. I've re-read it a few times, and will likely do so a few more times just to make sure it sinks in, but it definitely makes a lot of sense.
One thing I would say though is that I now feel Tactical Advantage is given too much focus on the match screen, perhaps implying it's more important than it actually is. The way it's displayed now does imply that the bigger the difference between the scores, the better the team will play, but clearly TA is just a small cog in a much larger machine. It wouldn't surprise me if others who have had issues with this side of the tactics setup think TA has a bigger impact than it does because of the way it's displayed.