So I got the fourth piece to my Tier 8 resto set last night. I guess what I was hoping for was to have a tic of rejuv happen at the very beginning when I cast my rejuv but it seems that the instant heal is a completely independent spell. Here's the post I've put on my guild forums with the pertinent information.
Description: Your Rejuvenation spell also provides an instant heal for your target.
The amount of healing provided by this instant heal is NOT the same as your rejuvenation tics and is affected by few of the talents which Rejuvenation is affected by.
Formula: Healed Amount = 0.497(spellpower) + 373.3
This formula is based on a sample size of ~100 different spellpower combinations and includes the buffs provided by Tree of Life, Imp ToL, Imp MotW, Empowered Rejuvenation, and Master Shapeshifter. In total, the amount healed is roughly 3/4 of the amount healed by a rejuv tic.
Glyph of Rejuvenation: Does NOT proc from the instant heal.
The instant heal does not crit.
The following Talents do have an effect on the heal:
Imp MotW (albeit very minimally and only in ToL form)
Tree of Life form (the 6% healing bonus is taken into account for the heal)
Imp ToL (enhances ToL)
Master Shapeshifter (Only in ToL)
Empowered Rejuvenation (strangely this talent does have an effect on the heal)
The following Talents do not have an effect on the instant heal
Gift of Nature (I find it is as surprising to see this talent here as it is seeing Emp Rejuv up above)
I'm pretty sure my formula is incorrect but the numbers have worked out for me for the viable amounts of spellpower.
All in all, uber bonus even though it's slightly less uber than I had first envisioned.
Patch 7.2 for balance and resto druids
4 weeks ago