Note: This is not my own work but that of a Druid in my guild. I copy and pasted it from my guild's website as it seems like it might be something people would be interested in. Unfortunately he did not include the underlying math that brought him to these results but I can work on getting it from him.
By Lyoncet <Nameless> of Dunemaul.
The premises are this:
HT Build:
http://www.wowhead.com/?talent=MxcrzicsZZxxcuxqM0s
HoT Build:
http://www.wowhead.com/?talent=MzZZxEcteqrest
Full T5 gear with tier-five equivalent gear on off-set slots; tested this on the test server so numbers are actual, not theorycrafted. The gear comes out to 1282 +healing base and 383 spirit, which yields 27 extra mana/5 when not casting, 4 while casting, and 95.75 healing to the group if in Tree form. The int provides an extra 110 damage/healing if specced into Balance. Only Mark of the Wild was up when testing these builds. Additionally, the HoT build includes full ranks in Nature's Focus and Subtlety, while the HT build only has 3 points to split between these two.
Gear (for those interested) Full Tier 5, Lord Sanguinar’s Claim, Sunshower Light Cloak, Grove-Bands of Remulos, Girdle of Zaetar, Orca-Hide Boots, Naaru Lightwarden’s Band, Band of Halos, Ribbon of Sacrifice, Living Root of the Wildheart
As a side-note, I did not include in these calculations the set bonuses for the T5 set, which increase Regrowth's length by 6 seconds and add 150 to the bloom of Lifebloom, and also unequipped the provided idol that subtracts 29 from the mana cost of Regrowth.
I'll skip all of the math in terms of determening efficiency of spells, but I'll post the results that I found. I made up several healing sequences based loosely around the 21 seconds that Regrowth lasts.
http://i56.photobucket.com/albums/g1...t/hotspec1.png
http://i56.photobucket.com/albums/g1...et/htspec1.png
http://i56.photobucket.com/albums/g1...olsequence.png
http://i56.photobucket.com/albums/g1...cet/htspam.png
Of course, these are very loose guidelines for how healing will be conducted. There is lag, human error which makes it impossible to cast every spell exactly when the last spell/global CD is up, and extra spells such as Swiftmend and re-applying the HoT afterwords that did not make the calculations. Also, I know that you will not cast HT every time it is up as that would result in large amounts of overheal. However, the overall results should still be about the same between the different builds.
As you can see, at the moment (1a and 2a in the first two pictures), the HoT build has nothing in terms of healing on the HT build if they both use the same rotation of full HoTs along with HTs interspersed within. Whle the HoT build manages to squeeze out about 30 more healing, it's efficiency is 6.3 as opposed to the HT build's 6.8. However, when rolling lifebloom are made viable in 2.1, they will entirely shift the tables.
Sequences 2a and 2b in the first and second pictures demonstrate the first rotation in which the stack of lifeblooms is built. The healing efficiency of this sequence suffers somewhat while stacking the lifeblooms as you can see, but when that is established, they can move to sequences 1c2 and 2c2, where the only casts of lifebloom are to refreshing the stack one second before it expires. Once this happens, the mana efficiency of the HoT Druid dips a bit below that of the HT Druid, but the healing of the HoT Druid eclipses that of the HT Druid. However, since it is unlikely that either will be using HT every time it is in the rotation due to overheal potential, these numbers shift back to the typical HoT build doing greater efficiency and the HT build doing more healing per second.
Now, if we look at the last two pictures, we see two thigns. On the HT build, we have the sequence for nothing but HT spam. This gives almost equivalent healing per mana to the HT + Hots without rolling lifebloom sequence for the HT Druid, and also gives about the same healing/second. It gets less efficiency than the same spec's HT + rolling lifebloom + hots sequence, but only but 1 healing/mana and without the potential HoT overheal.
On the HoT build sheet, we see the stats for the Druid while in Tree of Life form. As you can see, while the healing/second drops considerably (about 950 healing/second as opposed to about 1650 on the HT-spam sequence), the mana efficiency jumps up to over 10.6 healing for every 1 mana spent. That's almost double the HT spam's efficiency. So while a HoT Druid in ToL form won't keep the tank up by him/herself, he/she will be able to, for very little mana, reduce the number of HTs and other direct heals necessary to keep the tank alive by a great number.
While a HoT Druid can certainly use lots of HTs and the HT Druid can stack up tons of HoTs, I think the best compromise is a "you do your job I'll do mine" approach to the task. You've got your HT Druid keeping the tank from taking more damage than the HoTs can heal, and you have your HoT Druid keeping the tank at the level where he/she rarely needs HTs. This way, the HT Druid can keep from running OOM and the HoT Druid has all the help he/she needs in churning out that little extra to keep the tank alive. (The Tree Druid's HoT rotation only requires 89 mana every second, more than simple enough with decent mp5 and a fair-sized mana pool along with a few breaks where the HT Druid picks up the slack).