I'll run tests for it in Awakening.

Edit2: Test conclusions,

At an Internal level of 30 (the ILv cap on Hard mode), units will earn 1 exp from hitting but not killing an enemy. This does not depend on how much damage is dealt, and the unit's internal level is too high to determine if the enemy's class/level matters.

At an internal level of 1 (the minimum on all difficulties), the avatar earned 15 exp from hitting but not killing a level 1 base class enemy, and was not damaged by the enemy during engagement.

At an Internal level of 1, the avatar earned 10 exp from hitting but not killing a level 1 base class enemy, and was damaged by the enemy during the engagement.

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I suppose some revisions should be made to the exp formulas then. I'll work on it in a little bit.