Healing out of Proportions During Idol Dream
From what I've gleaned, the only things yah need are Idol Dream and a Healing effect. The first healing effect value typically locks into a Unit and every other source adds that value to it. I'm not 100% sure if Over Healing is necessary first or not, I've had mixed results and it's hard to pay attention to everything at once. At the very least regular intended Health Buffs (Not Overheals) by themselves don't seem to affect anything. The weirdest part is that the extra heal value doesn't always affect all sources of Healing; an example being yah will have Equality and Harp Player going nuts and Slice of Heaven is fine and another match that Slice of Heaven is the one going nuts. Another thing to note: Mind controlled Units can carry the Heal Value applied from their side, making whatever the new owner uses get Bonus Healing. The moment Idol Dream is gone, everything seems to fix right up though.
The display numbers are kinda doing whatever they want, randomly choosing one of the heal Values involved to display, though when one is chosen, it stays that way. Normally it chooses the Extra Heal Value but it's not always the case. Granted this is on my end so it could look different for someone else with different browsers/settings.