@prim0c: I must say that my experiences are extremely similar to your own. I probably use GHW more than you, but that's it. With AA included, at my current gear level (~6500 healing, 17% crit) a HS is almost exactly on par with GHW in terms of HPS and just a little less mana efficient (assuming Tidal Waves for each). However, more of that healing is attributed to a secondary target in HS's case due to the increased AA proc rate. Typically, I'm only casting HS when the extra .2 seconds or so might make a difference, or anytime that my target doesn't yet have AF. Otherwise, GHW averages out to nearly identical numbers, while being a lot more stable and a similar speed. Also, it isn't too common that I actually want the AA proc over the additional healing on the primary target from GHW, although this difference is slight either way.
I don't quite use Riptide on cooldown in theory, but in practice I nearly do. I keep it always rolling on the tank, and then if someone else takes a moderate hit, Riptide is my first response. Otherwise, I try and hold it to follow a UW/GHW sequence to exploit the 30% bonus further. I utilize UW nearly on cooldown, most often with HS if TW is still up (to maintain AF), otherwise with a regular GHW.
I'm still finding both Chain Heal and Healing Rain useful when used in moderation. If I know high damage is incoming, I'll gladly Healing Rain even with only 3 people in range.
I'm gearing much the same as well, to great success. I stack Int gems, then reforge (mastery, then haste) for Spirit wherever gear is lacking it, then I reforge to crit otherwise.
Recently, I've been thinking about TC a lot, and how to best incorporate it in a spec. It certainly doesn't seem mandatory, but I can see a really aggressive strategy rising from proper TC usage. I want to test
Talent Calculator - World of Warcraft at some point. From my heroic experiences, as much as I've loved my passive 15% speed, I don't find myself using the instant Ghost Wolf portion of the talent much at all. Instead, I'm normally busy tossing out Riptides and UWs on the run, or simply activating Spiritwalker's Grace. So I'm toying with the thought of ditching Imp GW for an Earthen Vitality enchant, as well as a point in Elemental Weapons, Nature's Blessing, and Blessing of the Eternals for a single point in Elemental Precision and TC. With my current spirit levels, that point provides me with almost 5% hit, and most importantly, I am comfortably over cap during mana tide. By synchronizing my tides with healing lulls (and I know they exist, I use potion of concentration all the time in heroics), I accomplish hit cap easily on a budget. Points in Concussion as well as Precision make TC almost always a gain even outside of Tide periods as well.
Given the incredible scaling potential of TC, I'm considering saving my Synapse Springs cooldown as well for Bolt spam, increasing it's value.