Many of the perks have a damage requirement to be leveled. For example, to level demolitions you need to deal 25k explosive damage. Does overkill damage count for this? For example, if an enemy has 50 health left, and I use an attack which deals 100 damage, will 50 points of damage be added to the level requirement, or 100?
It does not sadly. You only get credit for how much health the enemy has, not how much you did. Once you have gotten their health to zero, any damage that exceeds that amount would be lost to credit. For example, a clot has, let's say, 100 health and you shoot a grenade at it doing 200 damage. You would only get credit for the 100 health the clot had.