It depends on what you play. That is a decent combo for PVE; if that is going to be your main use for it, then I wouldn't change it. Zen gives stability, which doesn't hurt. Field Scout and Third Eye let you land all those high damage shots without getting surprised. If you were pushing PVE more, then you might reroll for the extra damage/fast reload perks, but third eye is hand for that as well if you are playing more defensively.