Auto Attack top damage.

Why is it Unholys main damage source is auto attacks when we have one of the more slightly complicated rotations? here is my log from today on heroic Mother

https://www.warcraftlogs.com/reports/Cyk1vWQcDrHFZnmg#fight=2&type=damage-done&source=4

It's very obvious why we suck in PvE and PvP, If a mob or player moves away or gets kited we loss out on our top damage right?