That is a fascinating post, Vinod. I don't play a druid (yet), but I love figuring out numbers. Here's the arithmetic I came up with in regard to druid 29 healing, in comparison to all classes.
With no talents or gear bonuses (hps = healing per second i.e. throughput; hp%m = healing per % base mana i.e. mana efficiency, higher is better), here are all class healing spells for the 29 bracket. For the druid Regrowth spells, I split up the heal and HoT portions of Regrowth, which will help us do calculations later on:
542 avg heal, 216 hps, 14 hp%m (Druid, Healing Touch: 2.5 cast @ 38% base mana)
271 avg heal, 271 hps, 9 hp%m (Druid, Healing Touch (glyphed): 1.0 cast @ 29% base mana)
257 avg heal, 129 hps, 8 hp%m (Druid, Regrowth: 2.0 cast @ 33% base mana)
259 avg heal, 12 hps, 8 hp%m (Druid, Regrowth: 2.0 cast @ 33% base mana, HoT portion)
308 avg heal, 154 hps, 9 hp%m (Druid, Regrowth (glyphed): 2.0 cast @ 33% base mana)
(The glphed HoT is the same as the non-glyphed HoT)
244 avg heal, 20 hps, 12 hp%m (Druid, Rejuvenation: instant cast @ 21% base mana)
366 avg heal, 31 hps, 17 hp%m (Druid, Rejuvenation (glyphed): instant cast @ 21% base mana)
264 avg heal, 176 hps, 14 hp%m (Shaman, Lesser Healing Wave: 1.5 cast @ 19% mana)
408 avg heal, 163 hps, 13 hp%m (Shaman, Healing Wave: 2.5 cast @ 32% mana)
134 avg heal, 89 hps, 17 hp%m (Paladin, Flash of Light: 1.5 cast @ 8% mana)
426 avg heal, 170 hps, 13 hp%m (Paladin, Holy Light: 2.5 cast @ 34% mana)
286 avg heal, 191 hps, 14 hp%m (Priest, Flash Heal: 1.5 cast @ 20% mana)
286 avg heal, 191 hps, 16 hp%m (Priest, Flash Heal (glyphed): 1.5 cast @ 18% mana)
604 avg heal, 242 hps, 17 hp%m (Priest, Heal: 2.5 cast @ 36% mana)
245 avg heal, 16 hps, 13 hp%m (Priest, Renew: instant cast @ 19% mana)
245 avg heal, 20 hps, 13 hp%m (Priest, Renew (glyphed): instant cast @ 19% mana)
Let's make some sense out of these numbers. At first glance, the unglyphed HT has easily the best healing throughput of all the druid healing spells, and indeed of all class spells in the bracket except for the priest's Heal. Then, HT goes up even more with the glyph. But mana efficiency with regards to throughput drops by 36%. To heal exclusively with a glyphed HT would in effect cut off a third of a druid's total mana.
Next, notice that the hps for the normal HoTs of Regrowth and Rejuvenation together total 32 hps. If a druid glyphs Regrowth, then the total hps on top of the HoTs together maxes out at (20 + 154) = 174 hps. if a druid glyphs Rejuvenation, then the total hps maxes out at (31 + 129) = 160 hps. However, if a druid doesn't glyph either one, then the total hps maxes out at (20 + 129) = 149 hps. So as long as a druid glpyhs Regrowth or Rejuvenation, they'll be able to keep up with any other healer in the bracket.
Now the comparison. Let's say a druid glyphs for Regrowth, casts it, then Rejuvenation, then Regrowth again. That's the heal portion of a normal regrowth, plus rejuvenation, plus the heal and HoT of the second glyphed regrowth. 257 + 244 + 308 + 259 = 1068 healing, at 87% base mana. A glyphed HT, then Regeneration, then Regrowth yield 1031 healing at 83% base mana. So as far as total healing and mana consumption, these two series of heals are the same. But as far as cast time, the glyphed HT series is a bit quicker. Moreover, the glyphed HT means the druid can put the healing burst anywhere in the spell series, while the glyphed Regrowth cannot come at the beginning of the spell series.
For spell power bonuses (and I found this really interesting), HT gets 161% of spell power, which means glyphed HTs get half of that: 81%. Regrowth gets 54% + 19% for the HoT. This means glyphed HTs, even though they lose half their spell power bonus, still scale better than Regrowth when it comes to spell power. Note that it would take roughly +95 sp for a glyphed Regrowth to match the hps of an unglyphed, +0 sp Healing Touch. That's how much of a difference between Regrowth and HT we're talking about when it comes to hps.
As far as I can tell from the numbers, I see two basic healing strategies. First is the one Vinod discusses: the true power of druid healing is in the HoTs. Cast those first, then if you need some serious healing, land the HT which gives you pretty much the same healing-per-mana as the other spells. The second strategy is to glyph the HT so that it basically works like a fast Regrowth without the added HoT. The hps goes up to the same degree that mana consumption goes up.
In PvP, druid HoT healers will have better mana efficiency, and therefore more room to gear spell power. They won't have the burst healing that other classes do. Druid HT healers will have better hps and the best burst healing in the bracket, but will want to gear a lot more +INT.
A quick chart to provoke more thought....
Glyph, gear stat emphasis, optimal healing style
--------------------------------------
HT, +INT, plays like a paladin: bursty healing, lots of mobility.
HT, +sp, "glass cannon" druid healer.
Regr, +INT, off-healer, spams heals on the whole group from a distance.
Regr, +sp, plays like a priest: concentrate healing on two main targets.
Reju, +INT, off-healer, spams heals on the whole group from a distance.
Reju, +sp, quintessential druid HoT healer: maintain constant healing on three or four targets.
After looking up spells by level for druids, it looks like druid HT healers have the best advantages in the 39 and 69 brackets, while druid HoT healers do best in the 29, 59, and 69 brackets. ...WOW, a well-geared druid must wreak havoc in the 69 bracket.
Major caveat -- this is ALL play by numbers I did here. I have no real experience with druid healing, only shaman and priest healing. I defer to players with real experience to put this in perspective.
Thanks for the chance to play with WoW numbers!
Bwappo