Ok, spec first. Auracen mentioned the 18/0/53 build, in which you'd be going down Balance to max out Celestial Focus. Why? Your haste is still quite low in terms of achieving a 1 sec GCD, which dramatically increases throughput in 25s especially. Celestial Focus being maxed drops the haste needed for that almighty capped GCD from 856 to 735. Sexeh indeed while gearing up to there. Once you achieve the haste from gear, spec'ing out of CF to an 11/0/60 build is pretty much the norm.
As for gear, it looks like you're trying for haste wherever you can get it, which is good. BUT socket bonuses <<< 1 sec GCD in overall throughput. Try using a Nightmare Tear in your next head upgrade to keep that meta activated and fill any new upgrades with Reckless Ametrines only (unless you're at 856 haste ofc.) I know this may be difficult and counterintuitive. It will increase your effectiveness. Don't waste your time and gold regemming what you already have though, especially those items 245 ilevel and under, that you will likely/hopefully be upgrading. Try to attain your t10 4 piece, if you will be doing any 25-man raid healing ever. I actually kept wearing my 4t9 until I had the emblems and tokens to upgrade to 4t10 all at once. We can haz some OP set bonuses this expac. With the ICC buff up so high now, my PERSONAL gearing strat goes basically: haste to GCD cap > Spirit > Spell Power. Many folks would say I have my Spirit and Spell Power backwards. I prioritize regen over throughput because for me and my guild giving out my Innervates to our priests/pallies freely increases overall healing effectiveness. Once hitting a certain point in Spell Power (around 4k raid buffed) more just seems to tend to equate to an increase in overheal rather than raid survival. Plus there's no sweeter soup than being (one of) the last healer(s) standing on a brand new boss kill having frantically kept everyone up that last desperate 5%. When others have OOMed and died with their fancypants zomg max throughput (look! My Rejuv hits for 30 more than your Rejuv so I'm a better healer, rofl) setups I merrily kept spam casting without a care in the world for my manabar and the boss died.
I too bounce between raid and tank heals depending on the fight at hand and raid comp that night. I do so by swapping my Glyphs up, not my gear or spec (11/0/60,) and generally carry stacks of: Nourish, Wild Growth, and Rapid Rejuv. Only Glyph I never really swap is Swiftmend. Because eating another's Tree's HoT is just plain rude. I GENERALLY swap WG and RR for each other, but on certain fights it's more advantageous for me to drop Nourish for RR. Many Trees do not like Rapid Rejuv, I do like it for specific fights where damage is more concentrated and predictable via a debuff or such rather than splash or aura.
Playstyle varies by fight, but max throughput for aura damage fights (BQL, Sindragosa, etc) is going to be WG on CD with Rejuv spam in between. Maybe a LB on the current tank before you duck behind a tomb or something, and of course SM up ppl on the brink of death, but not much else. Tank healing depends, as so much else does too, on who you are healing with. Some fights and comps me being on tanks means rolling HoTs across all 3 like a BC Tree. I like doing that, makes me nostalgic for Hyjal. More often it means full HoTs on one or possibly two tanks with an itchy trigger finger hovering over Nourish and/or Swiftmend in between HoT reapplications. A lot of effective Tree tank healing, and any other class imho, comes down to being so familiar with a bosses' timers that you find yourself precasting a big heal without even looking at your boss mod because you KNOW that big ability is incoming. That usually only comes with grinding your face on said boss until you can't help but instinctively wince seconds before your tanks have gone splat so many times before. Or, you know, being very situationally aware.
