After we had some complaints about the hatch damage we investigated what the damage formula was and we noticed level difference wasn't taken into account at all. I cannot say since when this bug existed but we altered it now.
If the attacking kingdom is higher than both kingdoms in the defending alliance we compare to the highest kingdom and 5% less damage is done per level difference. The maximum damagereduction is 70% (so 14 levels lower).
We also slightly increased the damage done to high duration eggs.
I thought this bug was worth making an announcement over as it can influence a lot in wars.