Let's see... in general...
Straight Shot (*usually you need to keep this buff. ) + Bloodletter ->
Venomous Bite (*keep this dot) ->
Windbite (*keep this dot, and when 2 dots are critical, you have a 50% chance Bloodletter recast time will reset.) ->
Heavy Shot + Bloodletter (*I use a Macro: /ac "Heavy Shot" <t> /wait 1s /ac "Bloodletter" <t>) x N
-----------------------------------------------------------------------------------------------
If your friend need MORE dps, then, use buff.