Can't seem to find a thread directed at this particular issue. I've only recently hit 70 on my druid, and have specced full resto for healing.

On the official druid forums (which I probably shouldn't read anyway, as most of them seem a bit...off) I've read that healing druids have nasty aggro problems, which is something I have yet to experience personally. Posters claim various things. One suggests that healing proactively causes more threat than healing reactively, which seems to make no sense to me. I was under the impression that healing threat = ([amount healed]/2)/[number of enemies] per enemy, so I don't see why functionally it would make any kind of difference.

Others claim that Regrowth causes huge aggro, which again I do not understand as being specific to that spell (beyond it having a high crit rate talented, but critting in and of itself does not produce extra threat to my understanding).

There is also wild speculation as to how the threat from lifebloom is assigned.

Can anyone help me out?

I am speccd 11/0/50, fyi.

The lifebloom ticks (the HoT part) gives you aggro. The last big heal gives the target aggro.

I currently (this is only a problem for me really in 5mans, with few exceptions) use a Jewel of Charismatic Mystique to dump aggro when i need it. It has a six minute cooldown though, so it can't be used alot. It is probably my most used trinket by far.

Not very many people realize this aggro thing about lifebloom. You can check this out for yourself if you turn on KTM and do a lifebloom while you're healing. Just wait until you have no other HoTs ticking and watch the meters right as you hit lifebloom through until it blooms. It's obvious when you're looking for it.

So, to follow that, your healing threat as a druid only goes up alot if you have a bunch of HoTs ticking. Spamming Lifebloom won't net you alot of aggro cause the HoT part of it isn't big. Spamming Regrowth will, as will Rejuv (not so much as regrowth).

I don't know about Swiftmend, though I use it a ton in conjunction with Rejuv.

I rarely use regrowth, and i used healing touch once yesterday in a heroic during a boss. It was the first time I used it since i respecc'd to Resto some time ago.

I am a big lifebloom fangirl, as 40-50% of my heals come from Lifebloom, and the rest in Rejuv, Swiftmend, and way far behind those, Regrowth. I have been in a few different guilds' Kara runs in the last few weeks, and it always makes me wonder why Tree Druids spam Regrowth, as it is so mana inefficient and almost always results in overheal. I can totally understand in boss fights but i just have never used regrowth outside of boss fights really. I've seen quite a few tree druids do nothing but spam regrowth.

I don't know; I'd like to hear more on what everyone else thinks about this subject.

KTM is only as good ass the theorycrafting behind it. It is a guess based on what we know.

Wait till you get out of Karazhan and start doing some 25 man instances - i think you'll find the need to use those spells then. We're currently clearing the Lurker Trash and with 4 tanks all taking significant damage, including Mortal Cleaves, regrowth is a lifesaver - and HT becomes much more useful.
Of course, overusing Regrowth is incredibly mana inefficient and is very prone to generate a lot of aggro. I'd caution against using it unless necessary; or at least being aware of if it's needed and cancelling it at the last moment. You can usually be fairly efficient (and useful) keeping Reju and your lifebloom up; i like to think i'm providing a 'buffer zone' to the other healers, and topping up raid members who would not usually get healed.
Your choice to use a threat reduction trinket is perhaps a smart move - i know for a fact i could have avoided many deaths with one of those ^^ I'd love to see a change to druids to give us an active threat reduction spell/ability - Subtlety is just not enough.

In terms of aggro; yes druid healing is very aggro sensitive - we have no fade, no blessing of salvation, and no threat reducing totem. Ask any tank which healer they least want to take to heroic SH, can pretty much guarentee the answer will be a druid
The patch will only up our aggro generation due to the lifebloom improvement and this worries me quite a lot as i'm a very proactive healer and i use lifebloom and reju constantly. But at the end of the day, you are a healer and if the tanks cant keep the majority of mobs off you then they're doing something wrong

Most "druid healing threat" is due to aggro dumps on bosses. Often the first thing that happens after a knockback is a swiftmend/NS HT with other HoT's still rolling, and while we may be only doing 28% normal threat (.5*.7*.8) a 7k HT is still 2k threat, more than almost any other abilities are going to be doing in an instant.

These are all misconceptions probably. Regrowth is a spell that, with the right talents, crits a lot and people think "crit = a lot of aggro", which is in some way true because crits generally heal for more. But a normal heal for 2000 or a critheal for 2000 will both give you the same amount of threat. Didn't do any threat tests with Regrowth myself though.

Also, pro-active healing does generate less threat if, and only if, you cast it before you (and your target) goes into combat with a mob. You can put HoTs on a target, let him walk to a mob and the healing from that HoT won't give you any threat (tested this myself). So on big pulls, I always put 3x Lifebloom + Rejuvenation on the tank right before he walks in, which gives him a little bit more time to generate threat before I *have* to start healing.

This is a mere reflection. but I started to play with the fact that overhealing do not generate any aggro therefore I landed reg. on tank right after +combat tag.

MT pulls with ranged and I proactivly heals him with reg. which makes me aggro the rest of the pack (not pulled ones). Which makes me belive that overhealing does make some kind of threat, or the the fact that I did an action.

It could be something else (as I actually healed a tiny amount). But there is something to look at.

Regrowth buffs the person you cast it on with a HoT. I would assume that this is the cause of pulling agro, and also possibly the reason people "feel" that regrowth causes more agro than a MT of the same value.

Try pulling and then GoTWing a group as you get in combat, you pull agro just the same (I was ganked by trash in MC when we started raiding a few times before I figured out what was doing it, then again I was completely clueless back then).

I challenge this statement. a normal 2000 heal would give you 1000 threat and a crit heal for 2000 would give you 1500 threat. amarite or?

To the op: Unless proof is presented I think it's pretty fair to assume that it's all about the high amount of burst healing that a druid can put out and that it's got nothing at all to do with some druid heals generating more threat than they should. Combine lots of hots ticking and two near instant heals with agro dumping bosses or new adds spawning and no bos or instant deagro and you'll see a lot of overagros without it having anything at all to do with your healing spells causing more threat than they should.

edit: ah, hots don't generate agro per tick anymore or?

I think hots generate agro per tick, but any buffs put on while in combat will also generate agro (although very minimal afaik).

I'm a HoT-spamming tree druid. The only times I've had aggro problems are during aggro dumps, when CCs break and aren't picked up, and before I went HoTs and would crit a HT early on in a fight. (Crits do not seem to generate any more threat than that generated by the amount of increased healing for having crit... something you would expect to heal for 2000k instead gives threat for 3000k on crit.)

Anything that shows up in combat log counts as healing and counts as aggro generation. That includes overhealing done by statics. That does not include HoTs when the target is at full health.