I've also noticed that if the tactic isn't working and you're not churning out decent chances within 15 minutes or so, a change has to be made immediately (eg. original > MrH tweak) and most of the time, the tide will turn. Maybe it's because the formations are different, therefore switching catches the opponents' off guard, I also have an ASSALUT (dropping deeper with disciplined tight marking seems to work) that I tweaked as a backup tactic.
Maybe it's not news for you guys, I just rarely use different formations. I usually have a base tactic with attacking/defending variations.
Another thing, if a tactic is working but you're down on goals, you just have to persist and it will eventually work out. And if you don't park the bus on a slim lead in the last 5 minutes, the opponent is almost always certain to score.