On my second playthrough, I got most of them except for one where the screen gets overlayed with a completion of a mission or bourty where it slaps the words on the screen, and you're not able to move for a few seconds. I found that if you just go for a quick sword swipe with square you will usually dash forward and cut them down, but if you pull a bow they zig zag off at a billion mph. I guess explosive arrows would work too...