To test my theory, I compared the amount of balance taken by one swing of the same weapon with and without Balthite equipped. Both Champions have enough Channel Master to support their Balthite ranks.

Case A is a Champion with nearly 550 Balthus and 27 Dansel. That should contribute an additional 81 Balthus. The difference between the two cases is only 2 pixels, which equates to roughly 9 Balthus (2/124 [number of pixels in bar]*550), as far as I can tell.
Case B is a Champion with roughly 330 Balthus and 24 Dansel. That should contribute an additonal 72 Balthus. The difference between the two cases is 4 pixels, which equates to roughly 4/124 * 330 = 10.6 Balthus.
It seems to me like I measured something wrong, or made a bad assumption. Can someone point out my mistake? Is there actually a bug?
Thanks in advance.
-Usagi