Good point on Rune Tap, but for the love of sanity DS doesn't heal based on your HP. It heals based on the damage you take. In a Raid environment you are not going to be taking little enough damage for the minimum 10% heal to happen, especially on bosses where the VB glyph is the most likely to be useful.

I think the sacrifice of 3.75% RT heals is worth the extra 15% heal/absorb, if outside healing effects are actually going to increase the shield.

This is the post that you are looking for:
World of Warcraft - English (NA) Forums -> DK Tanking FAQ - UPDATED For 4.0.1

In a more general sense, I advocate ignoring Diseases entirely. The only exception to this is when you are in a Raid and no one else is providing the attack speed debuff from Frost Fever.

While I am not ignoring diseases entirely right now I am starting fights with a DS and a HS before applying diseases. With the loss of extra threat on IT I find that starting with diseases like I used to just doesnt work anymore.

Using the minimum versus 30% values, we can calculate the threshold where it leaves the minimum heal.

.3 * previous_damage = .1 * HP
previous damage = .1 /.3 HP = 33.33% HP

If you take more than 33.33% of your HP in damage over 5 seconds, the threshold is passed and you will no longer be healed for the minimum. We can easily test if Imp DS applies to the min by simply DS'ing before taking damage and seeing the damage we take before it's absorbed. (It isn't applied). We can also test the max by being hit for more than the threshold (it is applied).

We can also calculate the threshold it should come in at if the minimum is only supposed hold true until the Imp DS version takes over.

.435 * previous_damage = .1 * HP
previous damage = .1 / .435 * HP = 22.99% HP

If you strip off some gear, it is relatively easy to get a friend to hit you (in a duel) between those values. I've tried it and Imp DS wasn't applied. That's the easiest way to test it. Confirmation is always appreciated of course.

With the implementation of the new rune system being affected by haste, it has now become vitally important for DK tanks to avoid any/all boss mechanics that reduce haste. The haste reductions are currently negatively affecting the rune regeneration rate.

For instance, malleable goo on H Festergut will significantly reduce your haste, which cuts rune generation significantly. The most effective method I have devised for avoiding this is to turn the boss left/right to avoid the goo locations as the melee would in rotating between legs.

H Prof. Putricide presents similar problems with malleable goo but these are much less likely to hit the tank.

H Sindragosa's breaths have been similarly affecting rune regeneration rate - At the moment i can't think of a way of entirely avoiding each blast from her, AMS cooldown is too long to avoid them all, however I have heard (tho not tested yet) that blessing of freedom will remove the slow and haste reduction so you can generate runes at a regular pace. So the dk tank will have to suck up to some of the paladins in the raid to get freedom.

Not sure if this was a rhetorical statement or not, but I can definitely confirm that Imp DS does not apply to the 10% Health minimum.

You can test the Imp DS minimum heal issue on a target dummy, it's never been a question of IF it doesn't work but why it doesn't work, design or bug?

Also, it's difficult to confirm this with logs (the client and server don't seem to readily agree on when "the past 5 seconds" began and ended) so I don't have any evidence yet, but I'm reasonably certain that absorbed damage does not count towards the "heal for 30% of the damage taken".

That may seem intuitively obvious, but from a balance perspective it really should count, since a Pally or Warrior will block 30% of the damage and then subtract the absorb value while we do it the other way around, an obviously inferior order of operations.

Imp DS min heal: As you said it comes down to perspective. Design or bug. IMHO I would say Design as they set a lower bound of 10% health as a min. No dmg taken in 5s to calculate, no increase in healing from DS.

Absorbs: I can confirm absorbs DO NOT count.
World of Logs - Real Time Raid Analysis
[23:02:20.172] Sindragosa hits Melkor 16752 (O: -1, A: 12059)
[23:02:20.804] Sindragosa Frost Aura Melkor Absorb (3533)
[23:02:21.438] Melkor Death Strike Melkor +0 (O: 10015) <--- min 10% (+30% ICC buff) heal

We've been finding our MT pally's getting snapped since 4.0.1 to the point they used my DK alt and our druid ex-tank for sindi, warriors I'm told are in a similar light. My personal opinion is that DKs may end up getting some form of CD based change, we now have quite a number of substantial CDs on short timers.

As to Kaeth's post above I don't have any logs of damage falling without the figures outlined to test boundary case of Imp.DS kicking in unfortunately, so don't bother checking for possible ones. I'll try to keep an eye out for them.



EDIT: I did notice oddly enough that I got quite a few massive DS heals (~52k+) where I didn't take all that much damage and didn't have a GS on me either, was usually during VB (non-glyphed at that point).

I took 36319 actual damage inside previous 5sec, 11934 absorb, 2598 resist making a total with all 3 combined at 50851 damage.
36319*0.3*1.3*1.45*1.25(VB) = 25670 (floored value at each step)
If the damage received included resisted amounts then the healing from DS should have been 27507.
As far as damage reductions up at the time I had Blade Barrier 6% and Blood Armor 12%. No Inspiration/AncestralFort/PS/GS or any other buff that I can see that could be playing a part here. What I was wondering is can it crit, and is it a 1.5x crit if thats the case? Do % damage reductions reduce the damage taken but not the damage calculated for the heal?
[23:06:49.188] Melkor Death Strike Melkor +0 (O: 52507)

If you dive deeper into the logs you will notice that the blood burst from the worms does a rediculous amount of overheal despite the fact that they heal for so little. From my experience speccing into them they do not heal for near enough to make/break a fight (especially for the tanks that take such large hits) and the little amount that they do heal is on average between 60-70% overheal. When I fought blood queen last week with the raid taking constant dmg they still had 50% overheal. In my opinion this makes them completely worthless, at least at lvl 80 tanking, with these talents. Once Cata drops and we hit 85, with higher health pools and potentially more dmg thrown around, the worms may actually benifit the raid. For now, the logs just seem to prove them as not worth the points.

They literally try to heal everyone in range, as long as one person needs it. That is why the overhealing seems so high. If everyone in range had some health deficit, the healing is actually really high. To give you an example from Grukthar's log.
In most situations, you only have one or two people with a health deficit, so the overheal is huge. However, when you have 5 people or more with deficits, you get a decent chunk of healing.
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Edit: I've been trying to model mastery from a theoretical view (not our current view where you trade RNG avoidance for a shield you have some control over). I was wondering if you guys could help me verify this before I use it to start drawing exact numbers.
D = Damage
T = Time
A = Avoidance
DSI = Death strike interval (in seconds). Since the damage it mitigates is based on the previous seconds. The 5 / DSI generates our average uptime.
.2175 = .435 / 2 = Base shield mitigation
.0272 = .0625 * .4345 = Shield per point of mastery

Damage_Taken = D * T * (1 - A - {Base_Shield_Mitigation} - {Mastery_Mitigation})
Damage_Taken = D * T * (1 - A - { (1 - A)* .2175 * 5s / DSI } - { (1-A)* .0272 * M * 5s / DSI })

So, to compare mastery to avoidance, we compare 1 avoidance versus .99 mastery (.99 because of the rating difference).
DR= The amount of avoidance required to get the next point of avoidance

.01 / DR compared to Mastery_Mitigation or .99 * (1-A) * .0272 * 5s / DSI

That look correct to you guys?

I noted in the talent link provided early in the thread Bloodworms was recommended being taken. While being able to heal yourself thru yet another means might be situationally useful, in current Wrath end game I'd think its essentially worthless. I'll try to outline as best as I can.

A) Any group situation or raid you will have healers. The other tank classes may have some heal mechanic, but not close to Rune Tap (30 sec), Vampiric Blood (1 min), Death Strike (5 sec avg), Death Pact (2 min CD) & then Bloodworms to boot. Content is designed for those healers & those other tanks to get thru as well. Therefore, extra healing on the DKs part is superfluous, likely to result in only overheals on your part or your healers. If they cannot keep you & the group up they are not equal to the instance/raid. Spec'd right & geared similarly A DK shouldn't be taking appreciably more damage than the other classes.

B) A tank's main job is holding aggro, concentrating damage on themselves to make the healers life easier (not by doing their job, but by taking less damage than others classes from those same hits); directly in line with that is being able to take & survive hits. An ability that heals you is only useful as an "Oh Shit" button when healers maybe get silenced etc - but does nothing to contribute to your ability to take & survive the hit itself. It is also miniscule aggro at best, info on healing aggro DK's generate may be around somewhere, but I've never seen that proferred as a prominent feature of our selfhealing.

Bloodworms proc their heal at random, uncontrollable points in the fight. Therefore its irrelevant as an "Oh Shit" CD. I'd still call this a solo questing or PVP talent unless the damage they do consistently out performs Abomb's Might or BCB (and I won't profess to know that well as follows). I have 3 DKs at level 80 and tanked with all 3 specs prior thru out Wrath (Unholy early on, wasn't as viable later), my personal view was Blood was a bad tanking spec save for dedicated Boss Tank in a raid with very good people backing them up. Largely this was due to Frost having the mitigation & Blood having the healing - you can only heal yourself if you live thru the hit. Common occurrence back in TOC was a 45k health Blood tank died from a 45k hit while a 43k health Frost tank lived from a 42k hit after their mitigation differences. Then there was the AE aggro difference for all Not Boss stuff.

As of 4.0 the Mitigation of Frost & the Healing of Blood all reside in the one tree. However it remains that healing doesn't improve your ability to tank, self heals are really only good as CDs when you have competent healers on hand. Now when the Xpack comes out perhaps we'll see fights where a tank must heal themselves & even some on the group (like from Glyphed RT).

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Imp Bloodtap can be more useful since it can allow you to activate a major CD ability when Runelocked. However, I've found that I've never truly needed it in that regard. Mostly its just popping it to get another DS vs HS when most other runes were on CD. With the Sequential rather than Simultaneous refreshing on Runes its less likely you wind up in a situation where you can't use a CD because of Runelock and the time you might have the wait is essentially halved for a rune to come up. Most fights the use of CDs was a pre-planned thing, so it was and currently it fairly easy to time attacks to make sure your CD is up when say, Festgut inhales the 3rd time. Bloodtap has a 1 minute CD stock, personally I find that well enough for the rare occasions I find to use it.

Now it may be I am a shitty tank not using that ability, but I am thinking BCB & Abombs Might > Bloodworms & Imp Bloodtap. More threat (minor as it might be) vs healing I don't need or extra death rune every 30seconds that I can & have worked around in other specs. Its a matter of choice I suppose but until something necessitates it, I'd recommend changing those talents.

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EDIT:
@Lichloathe
I noted on your post on Blizzard forums you did not originally recommend taking Crimson Scourge. Since I was trying to spec out 13 diff level 80 toons I tried what you had down for expedience; I will say thats not a good idea unless you are only going to tank bosses. Thats from directly trying it out later that night.

D&D is now 30 seconds, no talent reduction, glyphed it has half that duration. Howling Blast is gone from tanking. Blood Boil is all you've got left that can be used frequently. Increasing the damage/threat, radius and getting a FREE proc when your are in a trash fight for more than 30 seconds (pretty much most large ICC pulls) I'd call this an essential. You might want to make that clear in your post at Blizz forums since here & there are probably 2 of the top sources people go to get their ideas on how to spec.