Maybe a screenshot of your UI to see what addons you have so we can give some info :PP like ForteXorcist , Gnosis , Weakauras , Affdots priest those are baseline... maybe not affdots but you get the point :P
1) looking at Sha: Your uptime is decent not too bad not too good :P Could have abit more but it's fine as it is You had 33 MBs in 263 seconds but you also had 26 DI proccs which means you prolly missed many of them or you were really unlucky and most of them overlapped real fast with each other.
On a side note: Why are you using DI on Sha? You have a huge amount of resources to procc ToF and not many adds that stay alive long enough for SWP to tick and to give you enough proccs for DI to outscale the huge uptime ton ToF.
I'll skip galakras since measuring DPS on that fight sucks :P
2) on IJ: DI is good for IJ indeed it's the right choice here :P Here in a 257 second fight you had 26 Mind Blasts which is less than perfect w/o DI. So you missed a pretty big amount of the 21 DI proccs you got. Dot uptime same as sha.. not spectacular not bad :P decent :P
3)Shamans: Again I feel like DI is weird on shamans since you can get ToF off every single add spawn and from the wolves in the begining. And since it's only 1 extra SWP I find it luckluster to ToF. But it's perfectly fine to be honest. Again though, you have 25 mind blasts in a 223 sec fight while also having 21 DI proccs meaning you missed many mind blasts. That could be due to trying to keep both dots on both shamans though. Your dot uptime is pretty good on this fight.
Also I see you have really low Mind Sear dmg, is it some strat your guild is pulling only having 2 people on the adds or did you just ignore them? :P Kill the adds save a life :P
Anyway so generally you should maybe fix your DoT uptime abit , and really work on using Mind Blast on CD. Clip everything for Mind Blast (well except if you have 3 orbs already where you should just DP and then instantly Mind Blast). That will give you more orbs > more DPs > more MFIs > more DPS :P Also since you're favouring DI over ToF you should be having many more MBs per fight.
Now about the gear. Since u're running 4piece as Cerbz said you should value crit=mastery.
Also you could check the "Fix My DPS" thread where more people give advice about min/maxing etc.