As mentioned with billmen, lowering this stat from 1.33 to 1 increased the kills significantly, actually allowing them to completely decimate cavalry. Going on that, and ignoring that it could very well be that just the 1.33 factor is just bugged.
If you look in the edu, all the bugged 2handed units(billmen, dismounted knights, varangians) have the 1.33 value, im changing it to 1 and seeing what effect it has.