Well how much healing do you think you should be putting out?
Looking at your spec it's a bit off, Absolution is kind of a waste, most disc priests go for Focused Will instead. Also innerfocus is a nice talent that you skipped. 2/5 in Divine Fury seems kind of pointless, 5/5 would be better, improved renew isn't really necessary.
Your gears a bit of a mess too.
Red Sockets = SP
Blue = SP = Spirit
Yellow = SP+ Intel
Don't gem for haste or MP5 as disc.
Ideally you want 2 spellpower trinkets, sliver of pure ice is nice, the 264 badge trinket would be a good replacemt for the talisman.
Both your rings need changing. You benefit little from haste and for some reason you have the DPS ICC rep ring.
Your boots have hit rating, get the crafted healer ones with spirit.
Your belt has hit and you bought it that way off the vendor, the badge healing one is good.
Your staff and wand also both have hit and need to be replaced with healing equivalents
In total you've geared for 294 hit rating. That's 294 items points that could go to improving your spellpower.
Very good advice from Mr. Winkle (makes me giggle typing that out).
A few things to mention on top of that:
- MP5 and Spirit are very similar. Maybe gem to a few Spirit bonuses to appease your Holy spec, but mostly SP for Disc.
- Use the Insightful meta, which has an incredible mana return. Other metas are for people with incredible ubergear (something that I lack too).
- Both specs need some work. The biggest issue is you need 3/3 Meditation in your Holy spec, or else you will be OOMing like crazy. http://www.wowhead.com/talent#bVcbhZsxtcbMqihhsuAo:N0m is the holy spec I've been using, feel free to play around with some of the extra points but it hits all of the core talents. http://www.wowhead.com/talent#bVcbuhhVRIsffRtbezc:bmA is the Disc spec I'm currently using - really the only optional points are the 5 between Holy Specialization and Desperate Prayer/Inspiration. Put them wherever, but Divine Fury as mentioned is a 5/5 or 0/5 talent.
Disc spec is perfect, holy is off. The greater heal talents are suboptimal, get rid of Improved Healing (and Divine Fury unless you're really attached to it) and drop some points in Empowered Healing. Instead, pick up Blessed Resilience and Empowered Renew. On any fight that has a constant pulse AoE, use Renew as filler spell instead of Flash Heal unless a surge is up. Also drop Glyph of Power Word: Shield in your holy spec and instead pick up Glyph of Guardian Spirit or Glyph of Prayer of Healing.
Healing has nothing to do with your gems. If your feeling like your not healing enough your gems are not the problem. Gems don't equal enough SP/Haste/Regen to be the deciding factor on anything. When I say this, what I mean is the difference between X gem vs Y gem. Obviously having a gem in each of your slots is gonna be very helpful, but using a Runed Cardinal over a Recklace Ametrine won't make or break you by any means.
If your not healing enough your answer is actually very very simple, heal more. The problem with healers these days is that they think that if no one is taking damage, there is no point in healing. I can't tell you how many healers I have seen that say "I don't have mana issues in raids, I start and end with 100% mana". Any healer that has no mana issues, and especially ends a fight with 100% mana, is simply not healing how they should be.
Think of healing much the same as DPSing, where you use every Global Cooldown you possibly can regardless if people are taking damage or not. Proactive Healing VS Reactive Healing is what keeps people alive. As a Discipline priest this is particularly effective, as shields can be cast even if the raid are all topped off. If you are sitting around for 4 seconds after every single spell you cast, you are not healing correctly.
Here is a log of my most recent WoL parse. I am a Discipline Priest just like yourself.
I notice some people are worried about Overhealing, or Mana Issues when spamming an entire fight. For Overhealing... if people aren't dying, and you aren't running oom, then overhealing means absolutely nothing. As far as mana issues, gem/Enchant for it. Only until you can comfortably go an entire boss fight without going oom (Including using your own Mana Regeneration Tools, Shadow Fiend, Divine Hymn) should you worry about making your heals bigger. As it stands people very rarely die from X heal wasn't big enough, they die to not receiving a heal in time, or at all.