I have been playing my shadowpriest since the end of WOTLK. My ratings are bleh as I came back towards the end of last
season, so just bouncing around team to team to get points, mostly doing BG's for fun. But...for what its worth.
Hit (until 6%)
Void Tendrils: Most people prefer Psyfiend, but I got tired of 90% of people just getting out of range. Its Ineffective against healers
unless you catch him LOS'ing their DPS, but in BG's especially most melee just sits in it while i destroy them.
Currently using Phantasm, but with the recent nerf it is inifinitely less useful, and I find it not actually making me immune to slows/roots
a pretty good portion of the time but the other abilities in this tier are still pretty shitty imo.
From Darkness Comes Light. Still my preference. I tried Solace and Insanity and preferred the instant mind spike dmg as opposed to channeling
a mind flay, Also i found myself getting very frustrated when silenced after popping a 3 orb DP.
Angelic Bulwark. This is just a preference in my eyes. I like the idea of me not having to use a GCD for desperate prayer, and Ive pretty much
used up all my convenient bindings as is.
Divine Insight. The extra MB procs are great for burst, building orbs.
Cascade. Again, just my personal preference. I started with Halo because thats what everyone else used, but its easy to LOS which annoyed me.
Cascade will also self heal when it bounces assuming you target a teamate.
Dispersion. 15 second reduction in my O-Shit button and mana regen.
Dark Binding. Saves a GCD every time you need to heal.
Mass Dispel. With the nerf to mind spike glyph, this is what I've settled upon for the time being. MD'ing a pally bubble before he gets off a
heal is pretty satisfying. I tried Psychic Horror glyph, but didnt really see as much benefit.
As far as rotations...there isnt a set rotation in PVP its all situational. But 9/10 ill start with VT and SW:P, Mind Blast on CD until I get to 3 Orbs. If I'm playing offensively I'll use my fear and Blood Elf racial and Psychic Horror to interupt until 50% or so HP. Reapply dots, Then hit my silence, and my burst (3 ORB DP, any Mind Blast Proc, any Mind Spike proc, Shadowfiend if I'm below 50% mana, otherwise I save it) which will either kill them or force them to go defensive.
I recommend Void Tendrils against melee comps depending on how many root breaks they have - it's quite effective against warrior comps, it's ineffective against rogues. I ALWAYS take Void Tendrils against hunters, because when they blow all their cooldowns and stampede, they are deadly enough (especcially KFC, Warrior/Hunter/Healer) - Void Tendrils lets you root the stampede and possibly the warrior - and then deal with the hunters burst alone - it was the only way to beat KFC's last season (if you didn't have a frost mage for frost nova spam).
Psyfiend I take against caster comps usually - it does often get either nuked or ranged - but it can be useful for defining position / peeling during enemy burst - when they pop cooldowns throw it down and they either need to swap and punch it, or range it (waste CD time) or get feared.
Dominate Mind can be amazing, especcially on Blade's Edge and Dalaran. With the reduced cooldown I expect to try this a lot more (but I was already using it against certain comps last season, even though apparently I was the only one using it).
I recommend Mindbender actually, Mindbender supplies some useful tricks like putting it on a healer who is sneaking off to drink to keep them in combat - it also front-loads a good deal of burst into a GCD many seconds before your burst damage goes out. And it mitigates the risk of Shadowfiend getting CC'd and not returning mana - by being up way more often (so not worth bursting or CC'ing like Shadowfiend).
Divine Insight or Power Infusion (depends on your comp). I use Divine Insight, when multi-dotting for pressure the extra procs give you lots more DP -and DP is everything to us now. Power Infusion gives you a much stronger burst window though, and if I were running Shadow/Frostmage/Healer, or Shadow/Warrior/Healer - I'd be considering PI. Syncing your burst with your teammates burst is very powerful - but PI only really becomes impressive when you can free-cast, and that means your partner has to CC everything for you by themselves (hence Fmage or Warrior).
For glyphs, I recommend:
Mass Dispel (only one I often consider mandatory) - the real use of this is not as Celebrate suggests to MD immunity effects like bubbles - it's for mass dispelling your healer out of magic CC's (poly, fear, etc) - without the glyph it makes you susceptible to kicks and knockbacks and cc's during the cast, when MD'ing out of fear it's hard enough when they're running around to hit an 0.5s targetted cast, MD'ing a teammate out of fear with 1.5s cast is at best unreliable and at worst impossible.
Depending on what comp you are running (if you are often the kill target), and what comp you are fighting (melee cleave vs spell cleave) I often run either Inner Fire or Inner Sanctum - it's not a ton of surivability - but especcially if you expect to be the one getting hit on your team, it lets us tailor our defense to counter enemy comps. Very effective.
Dark Sanctum - if I expect to be ProM'ing or renew a lot, but generally this glyph I'm not a fan of now. If I need to heal someone - it's Flash Heal - and this glyph doesn't let us Flash Heal in Shadowform (unlike the Boomkin version which does let them Healing Touch in Laser Chicken form).
Vampiric Embrace - it's a massive healing button with the glyph, and it works regardless of who is being punched on your team. If we fight a pressure team (like Shadowplay, Shadowcleave, Unholyplay) I will always try to bring this glyph - when everyone on our team starts getting low at the same time - press this to turn off all their pressure for a bit.
Dispersion - I haven't used this glyph on protest that it's not -45 seconds now like it used to be. But, I suppose it's not terrible - I just hate it personally for not being what it was.