Oh.
I thought it was a deliberate choice from your current gemming choices (160 pure ints?

) im guessing its a work in progress as you arent even reaching the first haste breakpoint at the moment!
The enchants on gloves/legs/boots are weird too! You most definitely want haste on gloves, int/crit on pants (you are reforging away a ton of spirit so its a waste atm) and haste instead of pandastep on boots because it does not stack with glyph of mind flay, wich is one of the strongest indirect dps boosts you have
I dont mean to sound too inquisitive (or like a dick if you prefer

) but i know how frustrating it is to get thrust into a raiding environiment where the majority of people has better/more optimized gear than you do and also a lot of experience with their class, so im trying to help in any way i can
Another suggestion is to watch a lot of videos with shadowpriest PoV for bosses
Generic tactics are one thing, using all the possible tricks of your class to squeeze more dps is another thing