I was thinking that myself. Beyond should also add damage to Light attacks, though if my memory is right I always felt it was lackluster as well. (Like doing 700-800 damage holy mist, and that it had 30 MAB as well so it seemed way too low)
But if you think about it holy was nerfed back in the days, so it could just be SE's old nerf kicking in that is in place to make WHMs less powerful. Perhaps Holy is simply "unmodifiable" since then.
