[Schatze]

You do know that after 4 kills on a person you get 0 honor from killing them subsequently right? It goes 100%-75%-50%-25% to 0.

You say 300 kills in 4 BGs. Assuming you only faced each person once, that's a max of 160 kills that actually added to your score. My bet, however, is that for the most part you were facing the same people, hence the low honor score.

Edit: and yeah the bonus was bugged. It might be fixed now though, or something changed at least.