Hellfire Assault and Iron Reaver were quite easy on Normal with a team in mostly H-BRF gear. Tuning is very light on these. Feel v. puggable.
Difficulty jump between normal Hellfire Assault and heroic Hellfire Assault seems massive, but appears to mostly be a gear thing. It's a fight that gets much easier as you get more gear, since it's mostly a "keeping up with adds" fight.