On gear, I would go crit = mastery rating.
In your logs, looking at try 3 since it is long, and only before your death. For you, this was a FDCL pull.
First on healing:
-PoM is not bad, especially when you need to use an instant due to incoming screech. Glyph it or don't, either way it'll provide a decent amount of healing. (I prefer not because DP keeps spriests up well enough, and raid healing is often better than tank healing).
-PWS on yourself is not a waste of a GCD either, especially as screech comes faster.
-you have a warlock in raid, but no healthstone usage. :(
-MB at 8.Xs intervals, pretty good.
-SWP uptime good, VT could use some improvement
-FDCL vs SWI. You got ~6.1m dmg from mind spike (maybe hindered by low VT uptime). Your average MF tick is 181k (this seems high to me; according to your logs every single MF tick procced a mastery tick), let's use 125k to be conservative. You would need roughly 45-50 SWI ticks to match your FDCL damage. You cast 9 DPs during the fight, so you would need to find 5-6 ticks or 2 full GCD of SWI per DP to break even. For me, I would choose SWI. You'll get at least 1-2 good SWI on pull when he is barely screeching, and should also get a few good ones in during transition against Thok or the gatekeepers.
I noticed that you seem to be hitting every bat with SWP. Depending on how fast you kill them, it is probably a waste of GCDs, and putting up that many SWP is going to GCD cap you trying to deal with DI procs too.