Icaruss whispered me at the start of 5.4, telling me that I should be running heroic Throne of Thunder, because the 4 set bonus is really strong with the new talents that 5.4 brought for druids (namely Glyph of Efflo).
I did tell him that I hadn't killed Lei Shen yet on normal, so there was no chance of me getting any heroic tier! And the thought of Tier seemed so far away. At the end of 5.4 I only had 3 pieces of Tier - Shoulders, Legs and Gloves.
The T15 set bonuses are:
2 set bonus: Swiftmend's ground effect can now heal up to 4 targets each time it heals
4 set bonus: The healing done by your rejuvenation increases by 6% each time it causes healing.
The T16 set bonuses are:
2 set bonus: Rejuvenation ticks have a 12% chance to grant a Sage Mender, reducing the mana cost and cast time of your next Healing Touch by 20%, stacking up to 5 times.
4 set bonus: Targets of your Wild Growth spell are instantly healed for (Spell power * 0.25).
You can see that they are very different in terms of the way you heal. For T15 it looks like you'd be blanketing rejuv a lot, whereas with T16 it's trying to make you use direct heals a lot more..
As I don't have the 4 set T15 bonus anyway, it seems logical to move to the new T16. It's the T15 4 set bonus that really edges out in heals, and I've noticed that many high end druids are using heroic T15 (Beru, Jasyla, Juvenate, as well as the resto druids in the top guilds on our server). But remember though, I am only a normal druid doing normal raids, so it's a little bit different!
I may actually have more luck getting the 4 set bonus with us running Flex and normals. I think in a 10 man raid, you don't miss the extra efflorescence target as much because you really don't have that much melee or people stacking in the Efflo, compared to 25.
But this week has only had 2 days and I managed to get 6 upgrades - I got my first drop from Ordos, I got Tier from a Celestial, and I rolled a warforged neck and got a new trinket in raid on Wednesday. Tonight I upgraded my weapon from a roll, and also won the ring! Where 2 weeks ago I was having difficulty reaching the 13163 haste break point, and just reforged and regemmed everything for mastery with a haste of 3042, now I have suddenly shot way over it, and have to go reforge and regem AGAIN!
Why am I trying to reach that crazy haste anyway? At 13163 I get a second extra tick of Tranquility. At 3043, I get one extra tick. There are a lot of extra Wild Growths, Lifeblooms and Rejuvenations in the in-between haste break points but they're not really very exciting compared to another tick of Tranquility.
I was never a big fan of Soul of the Forest, as it was a mana chewer, but I have really loved it in 5.4. With the new glyph of Efflorescence, I can have that going somewhere and also have my hyper hasty wild growths or lifeblooms on raid or tanks and it's quite fun. Sev has been trying to make me do the swiftmend + rejuv + genesis for a fast heal but I've found genesis much more useful for charging up mushrooms for big AOE heals for stacked groups. However, I have NOT found Soul of the Forest to be as wonderful for Arena. I feel like I lack the bursty heals that come from tree form glyphed regrowths - 4 regrowths in tree form seem to feel more satisfying than casting a rejuv + swiftmend (IF it's up!) + rejuv + genesis. So, I run around doing Soul of the Forest in PvE, and Incarnation:Tree for Arena and PvP. I know there are people out there using SotF for arena and doing well at it, but I just don't find it that wonderful against a triple DPS or strong burst team. It is however great against a dot team constaining a combination of afflock/boomkin/shadowpriest.
I am eager to try out the 2 set bonus in Proving Grounds. Anything that conserves mana there should be rather useful - especially if it makes my Healing Touches faster. It will change the way I've been healing (I was a little more rejuv heavy but this may make me do directs more, which is rather weird) but as with all things, there is more than one way to heal, and having these two very different Tier bonuses demonstrates just that.