I've gotten some good ironite return from tier 5. I've been leveling 4 and 5 star hearts about halfway and it's been pretty good.
This event has been great! With the gold return, it's not a drain on that resource, which is awesome. And stockpiling some ironite has been a plus. Heroic souls and especially mythical heroic fragments are what I need, so I keep feeding the oven. Finally got the 4 star ninja assassin who had eluded me.