On paper / high gear level + perfect play:
int >> haste to breakpoint > mastery > crit > spirit > haste
Lower gear level + comfortable playstyle:
int >> haste to breakpoint > mastery = crit = spirit > haste
i.e. just pick the highest ilvl item, note your haste rating, and enjoy.
Rough scaling factors:
Int: 1
Spell Power: 0.47
Spirit: 0.40
Crit: 0.43
Mastery: 0.47
Haste: N/A (depends what you reforge it into)
How much spirit?
While spirit is the worst stat on paper (by a very small margin), in practice not every point of health healed is equal. You want enough mana not to go oom while healing what you have to. Up to Spine you can get away with minimal amounts of spirit, but you need mana for both Deathwing encounters.
Around 2600-3000 spirit should be in the comfort zone for those.
Haste rating?
Breakpoints worth gearing for:
916 rating
2005 rating (1573 DI)
3754 rating (3272 DI)
These assume proper raid buffs, which you should really have. Always gear to a breakpoint. For example: 916-940 is fine, 915 is VERY wrong, 1300 is wrong.
You should be able to reach 2005 rating with ease now. Haven't calculated how much you should be willing to sacrifice for 3754 rating, but it's unlikely you'll be able to comfortably reach that for a while still.
Gemming?
Use the scaling factors to evaluate what to take. Generally you'll be doing pure +int in nearly all sockets. Use Burning Shadowspirit Diamond (http://www.wowhead.com/item=68780), it works with heals now.
Tier gear?
More info in here: http://www.paragon.fi/forum/viewtopic.php?f=29&t=2978
Short summary: Stick with 391 t12 until you have at least 3 pieces of 410 heroic gear. If you don't have 391 tier, upgrade to 4t13 when you have 403 pieces.
Glyph of Wild Growth?
Short answer: use it if you're doing 25-mans, consider using it if you're doing 10-mans.
Talents?
Choose your poison:
For lower ilvl progress: http://wowtal.com/#k=gsuYHS6L.b0w.druid.
Nature's Bounty and no dispel: http://wowtal.com/#k=gsubSadB.b0w.druid.
Heroic progress for geared peeps: http://wowtal.com/#k=gCNDR9v8lB.b0w.druid.
Recount is my raid frame: http://wowtal.com/#k=gj-_bQ3vG.b0w.druid.
Many of the talents are in practice very near each other in value. Consider what fits your situation, and don't be afraid to modify the specs to suit your taste.
Never take points away from the following, unless you know what you're doing:
Natural Shapeshifter, Naturalist, Heart of the Wild, Master Shapeshifter, Improved Rejuvenation, Revitalize, Malfurion's Gift, Efflorescence, Wild Growth, Gift of the Earthmother, Swift Rejuvenation, Tree of Life, Nature's Majesty, Nature's Grace, Moonglow
Further info?
Happy hotting.