I tried a dozen or more shots with a particular opponent, with and without Augment Damage (level 5), and there wasn't a significant difference (damage in the 5-25 range, similar distribution). With the variability in bow damage, though, it is possible it just didn't show up in the results. It is too bad neither item editor for the game can edit bows, as that would remove that problem. Another test with 20 or 30 data points per run, checking the average and standard deviations would be needed to confirm.
