It sounds like the ME hasn't changed but the way the computer implements its own tactics has changed which would explain why some tactics are not working the same even if the match engine is the same.
Indeed, very good point, but even so, that shouldnt "destroy" a tactic. If it all it takes is a slight AI adjustment to make it fall apart, it cant be that sound.
Good thing for some that the AI is relatively weak, if it was half as adaptive as us, it'd rip most of these tactics to shreds after about 20 minutes