Please look up the information in the original post on how you should be playing your class. It isn't up to the rest of us to fix your mechanics. If you are looking for hand-holding, please check out shadowpriest.com.
With this gear on my SPriest: Nothealer @ Kel'Thuzad - Game - World of Warcraft , I'm doing like 11~13k DPS on Boss Fights, sometimes 15k. The rotation I use is the one posted by the OP. (In target dummy my DPS doesn't even reach 10k.)
My DPS is too low for Bosses WITH THIS GEAR? (I know there's some unenchanted items, I don't want to expend with items under 353 ilvl).
Nothing too serious, because this gear is trash, but just want to check if I'm doing something wrong now, so I wont keep doing it later on.