I wasn't complaining, and I never even said it was hitting too hard, just that it hurt. It was difficult content, it should hurt. I think you're reading too much into my comment. Here are my logs from Heroic Kil'jaeden. We were scaled to 905 ilvl and the average melee attack against me was 3.36m (not counting melee attacks when I had Fel Claws on me). I feel like that's a pretty good definition of feeling like my shit was getting pushed in.
To your other point, can you get 100% uptime on IBF against one target or do you need multiple? When I tested it I wasn't getting nearly enough charges to get more than 25% uptime (using trinket, too), but I wasn't able to test it in a raid setting.