Well, it does actually make sense to have adjustments in two places. The 'damage' function is used whenever damage of any type is applied to a character. This includes things like traps, spells, etc., basically anything other than weapon attacks. If all adjustments are moved to 'one_hit', then every other method of doing damage will have no adjustments.
If you really want everything in one place, it might make more sense to move everything into 'damage'. Nonetheless you should think about the distinction that is made between damage adjustments that depend only on the fact that it is a weapon combat, and damage adjustments specific to a given character. It is possible that a given adjustment might only apply when fighting somebody, e.g. a reduction of damage based on the alignment of the attacking character.
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David Haley
Head Coder, Legends of the Darkstone
BabbleMUD Project
http://david.the-haleys.org