Need help bis Shadow dps

Hi

As the title says Im almost bis pve shadow priest (only missing hc phylactrey trinket from sindy)
Im exacting rotation as per guides

I open with : VT > DP > 1x MF > Inner focus > SW:Pain > then spam MF and refresh VT/DP when expiring (and SW:Death when moving)
Im also using flask (125 sp) and prepot with wild magic pot

Doing this for 2 months in multiple icc runs but still my dps is not very high (some shadow priests with same gear outdps me and some times lower sp outdps me)
my latency is about 150 ms

(Im hit capped too at 11% exactly 289 rating and my talents are like any shadow priest in end-game gear)
I want help if im doing any thing wrong
Thanks

Log those raids (check for world of logs guide on these forums) and compare yourself to the others, see what the difference is, what they are doing better.
Make sure you're not clipping your dots but rather refreshing AFTER they expire, ideally as soon as possible.
Don't inner focus for SWP, it won't benefit from it. Minor DPS decrease coz of that though, not the issue.
Use your shadowfiend.
Go through the comments of the guides and not just the guides, some good info there, some bad, so don't take it all at face value, try to think why some things are good and others bad.