[fortran]

The XP in def should reward only defs with intention to stop the atk, not 1 ship defs. The way it was nerfed was the laziest, but will reach the end that this feature will not be abused in the future.

But I would suggest something like that:
2000 x %Atk_Fleet_destroyed/emped x (Atk_fleets_value / Defense_fleets_firing_value) x (2 x Atk_fleets_value / Atk_planets_value)

%Atk_Fleet_destroyed/emped would measure effectiveness of the defense
Atk_fleets_value / Defense_fleets_firing_value to measure quality of the combat
2 x Atk_fleets_value / Atk_planets_value to try to contain abuses