Believe me I know, my total dps and scaled on some fights is ridiculous to say the least and afterwards comparing previous parses it comes down to crits and arrow splits.It is that simple, you're just experiencing randomness.
Rangers have the most flux in their damage than any other class in the game.
I parsed over a few weeks though, not just one zone or a few monsters. In the end my total dmg was better off with the ele arrows and far better off just learning to use the bandolier efficiently with bane arrows.
I truely wish shadowstorm was better, I mean its not like I haven't posted about it in the past.