If my dual buddy can't see the damage; what is to say that the damage is really there. I mean if an upheval does no extra damage (non-crit) on another player and with or without AF, it does the same amount of damage (takes my test buddy down to the same line in hp)I would have to say it is broken.
Do you read what players answer you ? You've got all the explanations on how this feat works and where to see the damage it gives in the ubove posts.
It does show on parse/combat log, but not as damage you did. As it is counted as damage your opponents inflict on themselves, you must look at the damage done by your opponent and not by you.
I tested this by myself and my buddy doing white hits (while I had AF on) there was no difference in hp loss when I did it with or without AF.